/** @file  ../include/unistd.h

 @internalComponent

 */

 /** @fn  access(const char *fn, int flags)

 @param fn

 @param flags

 @return   Upon successful completion, the value 0 is returned; otherwise the

 value -1 is returned and the global variable errno is set to indicate the

 error.

   The access system calls check the accessibility of the file named in the fn argument for the access permissions indicated by the flags argument.

  The value of flags is either the bitwise-inclusive OR of the access permissions to be 

 checked (R_OK for read permission, W_OK for write permission, and X_OK for execute/search permission), or the existence test ( F_OK. )

  For additional information on file access permissions see File Access Permissions.

 Examples:

 @code

 /* Detailed description: This sample code checks read-ok accessibility of file Example.c

  *

  * Precondtions: Example.txt file should be present in working directory.

  */

 #include <unistd.h>

 int main()

 {

   if(access("Example.c" ,R_OK)  < 0)  

   {

     printf("Read operation on the file is not permitted") ;

     return -1 ;

   }

   printf("Read operation permitted on Example.c file") ;

   return 0 ;

 }

 @endcode

  Output

 @code

 Read operation permitted on Example.c file

 @endcode

 Limitations:

 The fn parameter should not exceed 256 characters in length. 

 KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @see chmod()

 @see stat()

 @capability Deferred @ref RFs::Entry(const TDesC16&, TEntry&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  chdir(const char *_path)

 @param _path

 Note: This description also covers the following functions -

  fchdir() 

 @return   Upon successful completion, the value 0 is returned; otherwise the

 value -1 is returned and the global variable errno is set to indicate the

 error.

   The path argument points to the pathname of a directory.

 The chdir system call

 causes the named directory

 to become the current working directory, that is,

 the starting point for path searches of pathnames not beginning with a slash, ‘/.’

  The fchdir system call causes the directory referenced by the file descriptor fd to become the current working directory, the starting point for path 

   searches of pathnames not beginning with a slash, ‘/.’

 Examples:

 @code

 /*

  *  Detailed description   : This test code demonstrates usage of chdir system call

  *

  *  Preconditions : "Example" directory should be present in current working

    directory.

  */

 #include <unistd.h>

 int main()

 {

   if(chdir("Example") < 0 )  

   {

      printf("Failed to change working directory");

      return -1 ;

   }

   printf("Working directory changed");

   return 0 ;

 }

 @endcode

  Output

 @code

 Working directory changed

 @endcode

 @code

 #include<unistd.h>

 #include<stdio.h>

 int test_fchdir()

 {

    int retVal;

    int rmdr;

    int mkdr = mkdir("test_dir", S_IWUSR);

    if( !mkdr )

    {

      int opn = open("test_dir", O_RDONLY);

      if( opn != -1 )

      {

        retVal = fchdir( opn );

        if( !retVal )

        {

          printf("Fchdir passed");

        }

        else

        {

          printf("Failed");

        }

        int cls = close(opn);

      }

      else

      {

        printf("Failed");

      }

      rmdr = rmdir("test_dir");  

    }

    else

    {

      printf("Failed");

    }

 }

 @endcode

  Output

 @code

 Fchdir passed

 @endcode

 Limitations:

 The path parameter should not exceed 256 characters in length. 

 KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @capability Deferred @ref RFs::SetSessionPath(const TDesC16&)

 @capability Deferred @ref RFs::Att(const TDesC16&, unsigned&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  chown(const char *path, uid_t owner, gid_t group)

 @param path

 @param owner

 @param group

 Note: This description also covers the following functions -

  lchown() 

 @return   These functions always return 0.

  The chown and lchown functions are build supported but not available functionally.

  Symbian OS does not support the concepts of multiple users and groups.

 Limitations:

 KErrNotReady of symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  close(int fd)

 @param fd

 @return   The close() function returns the value 0 if successful; otherwise it returns 

 the value -1 and sets the global variable errno to indicate the error.

   The close system call deletes a descriptor from the per-process object reference 

 table. If this is the last reference to the underlying object the object will 

 be deactivated. For example, on the last close of a file the current seek pointer associated with the file is lost; on the last close of a socket any file descriptor for that file is closed by that process.

 If 'fd' refers to a shared memory object that is still referenced at the last close, the 

 contents of the memory object persists till it is unreferenced. 

 If this is the last close of the shared memory object and the close results in unreferencing of the memory 

 object and the memory object is unlinked, (only in this scenario) the memory object is removed.

  When a process exits all associated file descriptors are freed. As there is 

   a limit on active descriptors per processes the close system call is useful when a large quantity of file descriptors 

   are being handled.

 Examples:

 @code

 /* Detailed description   : This test code demonstrates usage of close  system call

  *

  * Preconditions :  None.

  */

 #include <stdio.h>

 #include <unistd.h>

 #include <sys/types.h>

 #include <fcntl.h>

 int main()

 {

   int fd = 0;

   fd = open("Example.txt" , O_CREAT | O_RDWR , 0666);

   if(fd < 0 ) 

   {

     printf("Failed to open file Example.txt");

     return -1;

   }

  if(close(fd) < 0 )

  {

    printf("Failed to close  file Example.txt");

    return -1;

  }

  printf("File Example.txt closed" );

  return 0;

 }

 @endcode

  Output

 @code

 File Example.txt closed

 @endcode

 @see accept()

 @see fcntl()

 @see flock()

 @see open()

 @see pipe()

 @see socket()

 @see shm_open()

 @see shm_unlink()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  dup(int aFid)

 @param aFid

 Note: This description also covers the following functions -

  dup2() 

 @return   The value -1 is returned if an error occurs in either call.

 The external variable errno indicates the cause of the error.

   The dup system call

 duplicates an existing object descriptor and returns its value to

 the calling process ( newd = dup (aFid, ).); The argument aFid is a small non-negative integer index in

 the per-process descriptor table.

  The new descriptor returned by the call

 is the lowest numbered descriptor

 currently not in use by the process.

  The object referenced by the descriptor does not distinguish

 between aFid and newd in any way.

 Thus if newd and aFid are duplicate references to an open

 file, read , write and lseek calls all move a single pointer into the file,

 and append mode, non-blocking I/O and asynchronous I/O options

 are shared between the references.

 If a separate pointer into the file is desired, a different

 object reference to the file must be obtained by issuing an

 additional open system call.

  In dup2, the value of the new descriptor newd is specified.

 If this descriptor is already in use and oldd != newd, the descriptor is first deallocated as if the close system call had been used.

 If aFid is not a valid descriptor, then newd is not closed.

 If aFid == newd and aFid is a valid descriptor, then dup2 is successful, and does nothing.

  Limitation: 

 @code

 dup2(int oldfd, int newfd); 

 @endcode

 The return value of dup2 can be different 

   from the one user expected to be (newfd). Users of dup2 must therefor use the 

   return value of dup2 as the new allocated fd rather than the one passed in (newfd). 

   As described above, if dup2 is successful the newfd and return values are the 

   same, .

 Examples:

 @code

 /*

  *Detailed description : Sample usage of dup system call

  */

 #include <unistd.h>

 #include <fcntl.h>

 #include <stdio.h>

 int main()

 {

   int fd;

   FILE *Fil;

   int Newfd;

   fd = open("Example.txt" , O_CREAT | O_RDWR , 0666);

   if(fd < 0 )  {

      printf("Failed to open file Example.txt");

      return -1;

   }

   Newfd  = dup(fd );

   if(Newfd < 0 ) 

   {

     printf("Failed to duplicate file descriptor");

     return -1 ;

   }

   close(fd);

   close(Newfd);

   printf("New Duped fd is %d" , Newfd);

   return 0;

 }

 @endcode

  Output

 @code

 New Duped fd is 4

 @endcode

 @code

 /*

  *Detailed description : Sample usage of dup system call

  */

 #include <unistd.h>

 #include <fcntl.h>

 #include <errno.h>

 #include <stdio.h>

 int main()

 {

   int fd;

   FILE *Fil;

   int Newfd;

   fd = open("Example.txt" , O_CREAT | O_RDWR , 0666);

   if(fd < 0 )  {

      printf("Failed to open file Example.txt");

      return -1;

   }

   Newfd  = dup2(fd  , 4);

   if(Newfd < 0 )  {

     printf("Failed to duplicate file descriptor");

     return -1;

   }

   close(fd);

   close(Newfd);

   printf("New Duped fd is %d" , Newfd);

   return 0;

 }

 @endcode

  Output

 @code

 New Duped fd is 4

 @endcode

 @see accept()

 @see close()

 @see fcntl()

 @see getdtablesize()

 @see open()

 @see pipe()

 @see socket()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  dup2(int aFid1, int aFid2)

 @param aFid1

 @param aFid2

 Refer to  dup() for the documentation

 @see accept()

 @see close()

 @see fcntl()

 @see getdtablesize()

 @see open()

 @see pipe()

 @see socket()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  fpathconf(int fd, int name)

 @param fd

 @param name

 Refer to  pathconf() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getcwd(char *_buf, size_t _size)

 @param _buf

 @param _size

 @return   Upon successful completion a pointer to the pathname is returned. Otherwise 

 a NULL pointer is returned and the global variable errno is set to indicate the error. In addition, getwd copies the error message associated with errno into the memory referenced by buf.

   The getcwd function copies the absolute pathname of the current working directory

 into the memory referenced by buf and returns a pointer to buf. The size argument is the _size, in bytes, of the array referenced by buf.

  If _buf is NULL, space is allocated as indicated by size to store the pathname and the current working directory is

 returned as long as the _size bytes are sufficient to hold the working directory name.

 This space may later be free’d.

  This routine has traditionally been used by programs to save the

 name of a working directory for the purpose of returning to it.

 A much faster and less error-prone method of accomplishing this is to

 open the current directory ((‘.’) and use the fchdir function to return.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 #include <stdlib.h>

 #define BUF_SIZE 100

 int main()

 {

  //change directory to c:

  int c;

  long size = BUF_SIZE;

  char *buf = NULL;

  char *ptr = NULL;

  c = chdir("c:\");

  buf = (char *)malloc((size_t)size);

  if (buf != NULL && c == 0)

  {

   //call getcwd to fetch teh current directory

   ptr = getcwd(buf, (size_t)size);

   printf("getcwd returned: %s", ptr);

  }

  return 0;

 }

 @endcode

  Output

 @code

 getcwd returned: c:

 @endcode

 Notes:

  The getcwd function

 returns the default working directory as c:\\private\\XXXXXXXX (where XXXXXXXX is the UID of the process) as the default session path is

 initialised to c:\\private\\current_process'_UID, in case of Symbian OS.

 @see chdir()

 @see malloc()

 @see strerror()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getegid(void)

 Refer to  getgid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  geteuid(void)

 Refer to  getuid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getgid(void)

 Note: This description also covers the following functions -

  getegid() 

 @return   These functions always return 0.

   getgid and getegid are build supported but not available functionally. Symbian OS 

 does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getgroups(int size, gid_t grouplist[])

 @param size

 @param grouplist

 @return   These functions always return 0.

   The getgroups function build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getpgrp(void)

 Note: This description also covers the following functions -

  getpgid() 

 @return   These functions always return 0.

   getpgrp and getpgid are build supported but not available functionally. Symbian OS 

 does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getpid(void)

 Note: This description also covers the following functions -

  getppid() 

   The getpid system call returns the process ID of the calling process. Though 

 the ID is guaranteed to be unique it should NOT be used for constructing temporary file names for security reasons; 

 see mkstemp instead.

  The getppid system call

 returns the process ID of the parent

 of the calling process.

 Examples:

 @code

 /*

  * Detailed description : Sample usage of getpid system call

  */

 #include <unistd.h>

 int main() 

 {

   pid_t pid ;

   if((pid = getpid()) < 0 ) 

   {

      printf("getpid system call failed") ;

      return -1 ;

   }

   printf("pid of this process is %d " , pid) ;

   return 0 ;

 }

 @endcode

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getppid(void)

 Refer to  getpid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getuid(void)

 Note: This description also covers the following functions -

  geteuid() 

 @return   These functions always return 0.

   getuid and geteuid are build supported but not available functionally. Symbian OS 

 does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  isatty(int fd)

 @param fd

 @return   The isatty returns 1 if fd is an open descriptor connected to a terminal; returns 0 otherwise.

   This function operate on the system file descriptors for character special devices.

  The isatty function

 determines if the file descriptor fd refers to a valid

 terminal type device.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 #include<fcntl.h> //O_APPEND

 int main()

 {

  int x = isatty(0); //stdin (fd = 0)

  int y = isatty(1); //stdout (fd = 1)

  int z = isatty(2); //stderr (fd = 2)

  printf("{Expected: 1 1 1} %d %d %d", x, y, z);

  int i = isatty(5); //some invalid fd

  int fd_file = open("c:\some.txt", O_APPEND);

  int j = isatty(fd_file); //valid fd of a text file

  int fd_pipe[3];

  int p = pipe(fd_pipe);

  int k = isatty(fd_pipe[1]); //valid fd of a pipe

  close(fd_file);         

  close(fd_pipe[0]);      

  close(fd_pipe[1]);

  printf("{Expected: 0 0 0} %d %d %d", i, j, k);

  unlink("c:\some.txt");

  return 0;

 }

 @endcode

  Output

 @code

 {Expected: 1 1 1} 1 1 1

 {Expected: 0 0 0} 0 0 0

 @endcode

 @see ioctl()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  link(const char *oldpath, const char *newpath)

 @param oldpath

 @param newpath

 @return   Returns 0 on successful completion. Otherwise returns -1 and sets errno to indicate the error.

   The link system call atomically creates the specified directory entry (hard 

 link) newpath with the attributes of the underlying object pointed at by oldpath. Note that if the link is successful the link count of the underlying 

 object is not incremented: On Symbian OS link functionality is simulated and the 

 underlying object is not aware of a existing link. Link is supported only on regular files and fifos. It is not on directories. Creation 

 of link on a existing link file is not supported.

  If oldpath is removed, the file newpath is also deleted as the platform recognizes the underlying object only by oldpath.

  The object pointed at by the oldpath argument must exist for the hard link to succeed and both oldpath and newpath must be in the same file system. The oldpath argument may not be a directory. Creation time stamp of the file 

   is not supported and access time stamp is equal to modification time stamp. 

   A newly created file will not alter the time stamp of parent directory.

 Examples:

 @code

 /*

  * Detailed description  : Example to create link to a file

  * Precondition : "Parent.txt" should exist in c: drive

  *

  */

 #include <unistd.h>

 #include <stdio.h>

 int main(void)

  {

     if(link("C:\Parent.txt","C:\Link") < 0)

     {

          printf("Link creation to parent file failed");

          return -1;

     }

     printf("Link to parent file created");

     return 0;

  }

 @endcode

  Output

 @code

 Link to parent file created.

 @endcode

 Limitations:

 - The oldpath and newpath parameters of the link() function should not exceed 256 characters in length. 

 - P.I.P.S. only simulates link files and does not distinguish between hard and symbolic links.

 - KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @see readlink()

 @see symlink()

 @see unlink()

 @capability Deferred @ref RFs::Delete(const TDesC16&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn lseek(int fd, off_t pos, int whence)

 @param fd

 @param pos

 @param whence

 @return Upon successful completion,  lseek returns the resulting offset location as measured in bytes from the beginning of the file. Otherwise, a value of -1 is returned and  errno is set to indicate the error.

 The  lseek system call repositions the offset of the file descriptor  fildes to the argument  offset according to the directive  whence. The argument  fildes must be an open file descriptor. The  lseek system call repositions the file position pointer associated with the file descriptor  fildes as follows:

 	If whence is SEEK_SET, the offset is set to offset bytes.

 	If whence is SEEK_CUR, the offset is set to its current location plus offset bytes.

 	If whence is SEEK_END, the offset is set to the size of the file plus offset bytes.

 Some devices are incapable of seeking. The value of the pointer associated with such a device is undefined.

 If 'fd' refers to a shared memory object then lseek() on the shared memory object is supported by the current implementation.

 Note : lseek function allows the file offset to be set beyond the existing end-of-file, data in the seeked slot is undefined, and hence the read operation in seeked slot is undefined untill data is actually written into it. lseek beyond existing end-of-file increases the file size accordingly.

 Errors:

 The  lseek system call will fail and the file position pointer will remain unchanged if:

 [EBADF]	The fildes argument is not an open file descriptor.

 [EINVAL] 	The whence argument is not a proper value or the resulting file offset would be negative for a non-character special file.

 [EOVERFLOW]	The resulting file offset would be a value which cannot be represented correctly in an object of type off_t(Not supported).

 [ESPIPE] 	The fildes argument is associated with a pipe, socket, or FIFO.

 Examples:

 @code

 /*

  * Detailed description  : Example for lseek usage.

  */

 #include <stdio.h>

 #include <sys/stat.h>

 #include <fcntl.h>

 #include <sys/types.h>

 int main()

 {

 int fd = 0;

  fd = open("lseek.txt"  , O_CREAT | O_RDWR , 0666);

   if(lseek(fd , 0 , SEEK_SET) < 0 ) {

      printf("Lseek on file lseek.txt failed \n");

       return -1;

   }

   printf("Lseek on lseek.txt passed ");

  return 0;

 }

 @endcode

 Output

 @code

 Lseek on lseek.txt passed

 @endcode

 @see dup()

 @see open()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  lseek64(int fildes, off64_t offset, int whence)

 @param fildes

 @param offset

 @param whence

 @return   Upon successful completion, lseek64 returns the resulting offset location as measured in bytes from the

 beginning of the file.

 Otherwise,

 a value of -1 is returned and errno is set to indicate

 the error.

 For full documentation see: http://www.unix.org/version2/whatsnew/lfs20mar.html#3.0

 @see lseek()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  pathconf(const char *path, int name)

 @param path

 @param name

 Note: This description also covers the following functions -

  fpathconf() 

 @return   If the call to pathconf or fpathconf is not successful, -1 is returned and errno is set appropriately.

 Otherwise, if the variable is associated with functionality that does

 not have a limit in the system, -1 is returned and errno is not modified.

 Otherwise, the current variable value is returned.

 The pathconf and fpathconf system calls provide a method for applications to determine the current

 value of a configurable system limit or option variable associated

 with a pathname or file descriptor.

 For pathconf, the path argument is the name of a file or directory.

 For fpathconf, the fd argument is an open file descriptor.

 The name argument specifies the system variable to be queried.

 Symbolic constants for each name value are found in the include file \<unistd.h\>.

  The available values are as follows:

 @code

  _PC_LINK_MAX

  	The maximum file link count.

 _PC_MAX_CANON

  	The maximum number of bytes in terminal canonical input line.

 _PC_MAX_INPUT

  	The minimum maximum number of bytes for which space is available in a terminal input queue.

 _PC_NAME_MAX

  	The maximum number of bytes in a file name.

 _PC_PATH_MAX

  	The maximum number of bytes in a pathname.

 _PC_PIPE_BUF

  	The maximum number of bytes which will be written atomically to a pipe.

 _PC_CHOWN_RESTRICTED

  	Return 1 if appropriate privilege is required for the chown system call, otherwise 0. -p1003.1-2001 requires appropriate privilege in all cases, but this behavior was optional in prior editions of the standard.

 _PC_NO_TRUNC

  	Return greater than zero if attempts to use pathname components longer than

 .Brq Dv NAME_MAX will result in an [ENAMETOOLONG] error; otherwise, such components will be truncated to

 .Brq Dv NAME_MAX. -p1003.1-2001 requires the error in all cases, but this behavior was optional in prior editions of the standard, and some non- POSIX -compliant file systems do not support this behavior.

 _PC_VDISABLE

  	Returns the terminal character disabling value.

 _PC_ASYNC_IO

  	Return 1 if asynchronous I/O is supported, otherwise 0.

 _PC_PRIO_IO

  	Returns 1 if prioritised I/O is supported for this file, otherwise 0.

 _PC_SYNC_IO

  	Returns 1 if synchronised I/O is supported for this file, otherwise 0.

 _PC_ALLOC_SIZE_MIN

  	Minimum number of bytes of storage allocated for any portion of a file.

 _PC_FILESIZEBITS

  	Number of bits needed to represent the maximum file size.

 _PC_REC_INCR_XFER_SIZE

  	Recommended increment for file transfer sizes between _PC_REC_MIN_XFER_SIZE and _PC_REC_MAX_XFER_SIZE.

 _PC_REC_MAX_XFER_SIZE

  	Maximum recommended file transfer size.

 _PC_REC_MIN_XFER_SIZE

  	Minimum recommended file transfer size.

 _PC_REC_XFER_ALIGN

  	Recommended file transfer buffer alignment.

 _PC_SYMLINK_MAX

  	Maximum number of bytes in a symbolic link.

 _PC_ACL_EXTENDED

  	Returns 1 if an Access Control List (ACL) can be set on the specified file, otherwise 0.

 _PC_ACL_PATH_MAX

  	Maximum number of ACL entries per file.

 _PC_CAP_PRESENT

  	Returns 1 if a capability state can be set on the specified file, otherwise 0.

 _PC_INF_PRESENT

  	Returns 1 if an information label can be set on the specified file, otherwise 0.

 _PC_MAC_PRESENT

  	Returns 1 if a Mandatory Access Control (MAC) label can be set on the specified file, otherwise 0.

 @endcode

 Errors:

 If any of the following conditions occur, the  pathconf and  fpathconf system calls shall return -1 and set  errno to the corresponding value.

 [EINVAL]	The value of the name argument is invalid.

 [EINVAL] 	The implementation does not support an association of the variable name with the associated file.

 The pathconf system call will fail if:

 [ENOTDIR] 	A component of the path prefix is not a directory.

 [ENAMETOOLONG] 	A component of a pathname exceeded

 .Brq Dv NAME_MAX characters (but see _PC_NO_TRUNC above), or an entire path name exceeded

 .Brq Dv PATH_MAX characters.

 [ENOENT] 	The named file does not exist.

 [EACCES] 	Search permission is denied for a component of the path prefix.

 [ELOOP] 	Too many symbolic links were encountered in translating the pathname.

 [EIO] 	An I/O error occurred while reading from or writing to the file system.

 The fpathconf system call will fail if:

 [EBADF] 	The fd argument is not a valid open file descriptor.

 [EIO] 	An I/O error occurred while reading from or writing to the file system.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 int test_pathconf()

 {

    int fp = open("test_pathconf1.txt", O_RDWR|O_CREAT);

    if(fp != -1)

    {

      int n = pathconf("test_pathconf1.txt", _PC_LINK_MAX);

      if( n < _POSIX_LINK_MAX )

      {

        return -1;

      }

      else

      {

        printf("_PC_LINK_MAX value: %d", n);

        printf("Pathconf passed");

        return 0;

      }

    }

    else

    {

      printf("failed");

      return -1;

    }    

 }               

 @endcode

  Output

 @code

 _PC_LINK_MAX value: 1

 Pathconf passed

 @endcode

 Note:

 @code

  The current implementation of the functions pathconf and fpathconf considers only the following configurable variables. _PC_LINK_MAX _PC_MAX_CANON _PC_MAX_INPUT _PC_NAME_MAX _PC_PATH_MAX _PC_PIPE_BUF _PC_CHOWN_RESTRICTED _PC_NO_TRUNC _PC_VDISABLE   Also, these functions return the limits as required by the POSIX

 standard instead of the actual system limits determined on the run. 

 @endcode

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  pipe(int *fildes)

 @param fildes

 @return   The pipe function returns the value 0 if successful; otherwise the

 value -1 is returned and errno is set to indicate the error.

   The pipe system call

 creates a pipe, which is an object allowing

 bidirectional data flow,

 and allocates a pair of file descriptors.

  By convention, the first descriptor is normally used as the read end of the pipe, and the second is normally the write end, so that data written to fildes[1] appears on (i.e. can be read from) fildes[0]. This allows the output of one thread to be sent to another 

   thread: the source's standard output is set up to be the write end of the 

   pipe and the sink's standard input is set up to be the read end of the 

   pipe. The pipe itself persists until all its associated descriptors are closed.

  A pipe that has had an end closed is considered widowed. Writing on such a pipe causes the writing process to fail and errno is set to EPIPE . Widowing a pipe is the only way to deliver end-of-file to a 

   reader: After the reader consumes any buffered data, reading a widowed pipe 

   returns a zero count.

 Examples:

 @code

 #include <unistd.h>

 #include <stdio.h>

 int main(void)

 {

     int fds[2];

     if (pipe(fds) == -1) {

        printf("Pipe creation failed");

     }

     /* fds[0] - opened for read */

     /* fds[1] - opened for write */

     close(fds[0]);

     close(fds[1]);

     return 0;

 }

 @endcode

 @see read()

 @see write()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  read(int fd, void *buf, size_t cnt)

 @param fd

 @param buf

 @param cnt

 Note: This description also covers the following functions -

  readv() 

 @return   If successful, the number of bytes actually read is returned. Upon reading 

 end-of-file, zero is returned. Otherwise, -1 is returned and the global variable errno is set to indicate the error.

   The read system call

 attempts to read cnt bytes of data from the object referenced by the descriptor fd into the buffer pointed to by buf. The readv system call

 performs the same action, but scatters the input data

 into the iovcnt buffers specified by the members of the iov array: iov[0], iov[1], ..., iov[iovcnt-1].

  For readv the iovec structure is defined as:

  struct iovec {

 void   *iov_base;  // Base address. 

 size_t iov_len;    // Length. 

 };

  Each iovec entry specifies the base address and length of an area

 in memory where data should be placed.

 The readv system call

 will always fill an area completely before proceeding

 to the next.

  On objects capable of seeking, the read starts at a position

 given by the pointer associated with fd (see lseek )

 Upon return from read, the pointer is incremented by the number of bytes actually read.

 If 'fd' refers to a shared memory object then read() on the shared memory object is supported by the current implementation.

  Objects that are not capable of seeking always read from the current

 position.

 The value of the pointer associated with such an

 object is undefined.

  Upon successful completion, read, and readv return the number of bytes actually read and placed in the buffer.

 The system guarantees to read the number of bytes requested if

 the descriptor references a normal file that has that many bytes left

 before the end-of-file, but in no other case.

 Errors:

 The  read, and  readv system calls will succeed unless:

 [EBADF] 	The d argument is not a valid file or socket descriptor open for reading.

 [ECONNRESET]The d argument refers to a socket, and the remote socket end is forcibly closed.

 [EFAULT] 	The buf argument points outside the allocated address space(Not supported).

 [EIO] 	An I/O error occurred while reading from the file system(Not supported).

 [EINTR] 	A read from a slow device was interrupted before any data arrived by the delivery of a signal(Not supported).

 [EINVAL] 	The pointer associated with d was negative.

 [EAGAIN] 	The file was marked for non-blocking I/O, and no data were ready to be read.

 [EISDIR] 	The file descriptor is associated with a directory residing on a file system that does not allow regular read operations on directories (e.g. NFS)(Not supported).

 [EOPNOTSUPP] 	The file descriptor is associated with a file system and file type that do not allow regular read operations on it(Not supported).

 [EOVERFLOW] 	The file descriptor is associated with a regular file, nbytes is greater than 0, offset is before the end-of-file, and offset is greater than or equal to the offset maximum established for this file system(Not supported).

 [EINVAL] 	The value nbytes is greater than INT_MAX.

 In addition, readv and preadv may return one of the following errors:

 [EINVAL] 	The iovcnt argument was less than or equal to 0, or greater than IOV_MAX.

 [EINVAL] 	One of the iov_len values in the iov array was negative.

 [EINVAL] 	The sum of the iov_len values in the iov array overflowed a 32-bit integer.

 [EFAULT] 	Part of the iov array points outside the process’s allocated address space.

 Examples:

 @code

 /* Detailed description :This example demonstrates usage of read-system call, this

  * Example reads 10 bytes from a file specified

  *

  * Preconditions: Example.txt file should be present in C: and should contain

  * string Hello World.

  *

  */  

 #include <unistd.h>

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <fcntl.h>

 int main()

 {

   int fd = 0;

   char Buff[12] = {0};

   fd = open("C:\Example.txt" , O_RDONLY );

   if(fd < 0 )  {

      printf("Failed to open C:\Example.txt file");

      return -1;

   }

   if(read(fd , Buff , 11) < 11)   {

      printf("Failed to read specified number of bytes from file");

      return -1;

   }

   printf("file contains %s 

 " , Buff);

   return 0;

 }

 @endcode

  Output

 @code

 file contains Hello World

 @endcode

 @code

 /*

  * Detailed description: Sample usage of readv system call

  * Preconditions: Example.txt file should be present in working directory containing  Hello world   in it

  *

  */

 #include <stdio.h>

 #include <sys/types.h>

 #include <sys/uio.h>

 #include <fcntl.h>

 int main()

 {

   int fd = 0;

   struct iovec io_vec[1];

   char Buf[12] = { 0 };

   io_vec[0].iov_base  = Buf;

   io_vec[0].iov_len = 11;

   fd = open("Example.txt" , O_RDONLY );

   if(fd < 0 )  {

     printf("File open failed");

     return -1;

   }

   if(readv(fd , io_vec , 1) <  11 )   {

     printf("Failed to read fron Example.txt file");

     return -1;

   }

   printf("Read succes %s"  , io_vec[0].iov_base);

   return 0;

 }

 @endcode

  Output

 @code

 Read succes Hello World

 @endcode

 @see dup()

 @see fcntl()

 @see getdirentries()

 @see open()

 @see pipe()

 @see select()

 @see socket()

 @see socketpair()

 @see fread()

 @see readdir()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  rmdir(const char *_path)

 @param _path

 @return   The rmdir() function returns the value 0 if successful; otherwise the

 value -1 is returned and the global variable errno is set to indicate the

 error.

 The rmdir system call removes a directory file whose name is given by path. 

 The directory must not have any entries other than '.' and '..'.

 Examples:

 @code

 /*

  *  Detailed description: This test code demonstrates usage of rmdir systemcall, it removes directory

  *  Example from the current working directory.

  *

  *  Preconditions: Expects empty directory "Example" in current working directory.

  */

 #include  <unistd.h>

 int main()

 {

   if(rmdir("Example") < 0 )  

   {

      printf("Rmdir failed");

      return -1;

   }

   printf("Directory Example removed");

   return 0;

 }

 @endcode

  Output

 Directory Example removed

 @code

 @endcode

 Limitations:

 The _path parameter of the rmdir() function should not exceed 256 characters in length. 

 KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @capability Deferred @ref RFs::RmDir(const TDesC16&)

 @capability Deferred @ref RFs::Att(const TDesC16&, unsigned&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setgid(gid_t gid)

 @param gid

 Refer to  setuid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setpgid(pid_t pid, pid_t pgid)

 @param pid

 @param pgid

 Note: This description also covers the following functions -

  setpgrp() 

 @return   These functions always return 0.

   These functions are build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setsid(void)

 @return   These functions always return 0.

   These functions are build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setuid(uid_t uid)

 @param uid

 Note: This description also covers the following functions -

  seteuid()  setgid()  setegid() 

 @return   These functions always return 0.

   These functions are build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  sleep(unsigned int secs)

 @param secs

 @return   If the sleep function returns because the requested time has elapsed, the value

 returned will be zero.

   The sleep function suspends execution of the calling process until seconds seconds have elapse

  Time interval is internally represented using 32 bit value(range +-2147483647). 

   Any time interval greater 2147483647 returns 0 without sleeping. Hence Maximum 

   sleep time supported here is 35 minutes, 47 seconds.

 Examples:

 @code

 /*

  * Detailed description: This test code shows usage of sleep system call , here sample code

  * sleeps for 2 seconds.

  */

 #include <unistd.h>

 int main()

 {

   if(sleep(2) < 0 )  

   {

     printf("Sleep failed");

     return -1;

   }

   printf("Sleep successful");

   return 0;

 }

 @endcode

  Output

 @code

 Sleep successful

 @endcode

 @see nanosleep()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  sysconf(int name)

 @param name

 @return   If the call to sysconf is not successful, -1 is returned and errno is set appropriately.

 Otherwise, if the variable is associated with functionality that is not

 supported, -1 is returned and errno is not modified.

 Otherwise, the current variable value is returned.

 This interface is defined by -p1003.1-88 .A far more complete interface is available using sysctl.

 The sysconf function provides a method for applications to determine the 

   current value of a configurable system limit or option variable. The name argument specifies the system variable to be queried. Symbolic 

   constants for each name value are found in the include file \#include \<unistd.h\> . Shell programmers who need access 

   to these parameters should use the getconf utility.

 The available values are as follows:

 @code

  _SC_ARG_MAX

   The maximum number of argument to execve.

  _SC_CHILD_MAX

   The maximum number of simultaneous processes per user id.(Not supported)

  _SC_CLK_TCK

   The frequency of the statistics clock in ticks per second.

  _SC_IOV_MAX

   The maximum number of elements in the I/O vector used by readv , writev , recvmsg ,

  and sendmsg .

  _SC_NGROUPS_MAX

   The maximum number of supplemental groups.(Not supported)

  _SC_NPROCESSORS_CONF

   The number of processors configured.(Not supported)

  _SC_NPROCESSORS_ONLN

   The number of processors currently online.(Not supported)

  _SC_OPEN_MAX

   The maximum number of open files per user id.(Not supported)

  _SC_STREAM_MAX

   The minimum maximum number of streams that a process may have open( Not supported)

  at any one time.

  _SC_TZNAME_MAX

   The minimum maximum number of types supported for the name of a

  timezone.(Not supported)

  _SC_JOB_CONTROL

   Return 1 if job control is available on this system, otherwise -1.

  _SC_SAVED_IDS

   Returns 1 if saved set-group and saved set-user ID is available,

  otherwise -1.(Not supported)

  _SC_VERSION

   The version of -p1003.1 with which the system

  attempts to comply.(Not supported)

  _SC_BC_BASE_MAX

   The maximum ibase/obase values in the bc utility.(Not supported)

  _SC_BC_DIM_MAX

   The maximum array size in the bc utility.(Not supported)

  _SC_BC_SCALE_MAX

   The maximum scale value in the bc utility.(Not supported)

  _SC_BC_STRING_MAX

   The maximum string length in the bc utility.(Not supported)

  _SC_COLL_WEIGHTS_MAX

   The maximum number of weights that can be assigned to any entry of

  the LC_COLLATE order keyword in the locale definition file.(Not supported)

  _SC_EXPR_NEST_MAX

   The maximum number of expressions that can be nested within

  parenthesis by the expr utility.(Not supported)

  _SC_LINE_MAX

   The maximum length in bytes of a text-processing utility's input

  line.(Not supported)

  _SC_RE_DUP_MAX

   The maximum number of repeated occurrences of a regular expression

  permitted when using interval notation.(Not supported)

  _SC_2_VERSION

   The version of -p1003.2 with which the system attempts to comply.( Not supported)

  _SC_2_C_BIND

   Return 1 if the system's C-language development facilities support the

  C-Language Bindings Option, otherwise -1.

  _SC_2_C_DEV

   Return 1 if the system supports the C-Language Development Utilities Option,

  otherwise -1.

  _SC_2_CHAR_TERM

   Return 1 if the system supports at least one terminal type capable of

  all operations described in -p1003.2 ,

  otherwise -1.

  _SC_2_FORT_DEV

   Return 1 if the system supports the FORTRAN Development Utilities Option,

  otherwise -1.

  _SC_2_FORT_RUN

   Return 1 if the system supports the FORTRAN Runtime Utilities Option,

  otherwise -1.

  _SC_2_LOCALEDEF

   Return 1 if the system supports the creation of locales, otherwise -1.

  _SC_2_SW_DEV

   Return 1 if the system supports the Software Development Utilities Option,

  otherwise -1.

  _SC_2_UPE

   Return 1 if the system supports the User Portability Utilities Option,

  otherwise -1.

  _SC_PAGESIZE

   Returns size of a page in bytes.  (Some systems use PAGE_SIZE instead.)

 @endcode

  Note: Some of the  return values may not be posix compliant.

 Examples:

 @code

 /*

  *  Detailed description  : This test code demonstrates usage of sysconf system call , here it get max command

     line arguments that can be passed to process.

 */

 #include <unistd.h>

 int main()

 {

   int ret = 0 ;

   ret = sysconf(_SC_ARG_MAX) ;

   if(ret < 0 )  {

     printf("Sysconf call failed") ;

     return -1 ;

  }

  printf("Max command line arguments = %d" , ret) ;

  return 0 ;

 }

 @endcode

  Output

 @code

 max-number of commandline args supproted by system.

 @endcode

 @see pathconf()

 @see confstr()

 Bugs:

  The value for _SC_STREAM_MAX is a minimum maximum, and is required to be 

 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously small 

 and misleading number. 

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  unlink(const char *pathname)

 @param pathname

 @return   Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

  The unlink system call removes the link named by pathname from its file system.

  Symbian OS simulates links so there is no reference count and files are unaware 

   of links. Calling unlink on a file will always close the file, regardless of 

   whether there is another link.

  The pathname argument may not be a directory.

 Examples:

 @code

 /*

  * Detailed description  : Example to unlink a link file

  * Precondition : A link file by name "Link" should exist in

  *                c: drive.

  */

 #include <unistd.h>

 #include <stdio.h>

 int main(void)

 {

     char rdbuff[25];

     if(unlink("C:\Link"))

     {

          printf("unlink on link file failed");

     }

     printf("Unlink on link file succeeded");

 }

 @endcode

  Output

 @code

 Unlink on link file succeeded.

 @endcode

 Limitations:

 - The path parameter of the unlink() function should not exceed 256 characters in length. 

 - P.I.P.S. only simulates link files and does not distinguish between hard and symbolic links.

 - KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @see close()

 @see link()

 @see rmdir()

 @see symlink()

 @capability Deferred @ref RFs::Att(const TDesC16&, unsigned&)

 @capability Deferred @ref RFs::SetAtt(const TDesC16&, unsigned, unsigned)

 @capability Deferred @ref RFs::Delete(const TDesC16&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  write(int fd, const void *buf, size_t cnt)

 @param fd

 @param buf

 @param cnt

 @return   Upon successful completion the number of bytes which were written

 is returned.

 Otherwise a -1 is returned and the global variable errno is set to indicate the error.

 The write system call attempts to write cnt bytes of data to the object referenced by the descriptor fd from the buffer pointed to by buf .

 The writev system call performs the same action, but gathers the output data from the iovcnt buffers specified by the members of the iov array: iov[0], iov[1], ..., iov[iovcnt-1].

 The pwrite and pwritev system calls perform the same functions, but write to the specified position in the file without modifying the file pointer.

 Notes: 

 1. This description also covers the pwrite(), writev() and pwritev() functions.

 2. An attempt to write on a broken pipe generates the SIGPIPE signal, which may cause termination of the process, if it is not handled.

  For writev and pwritev, the iovec structure is defined as:

 @code

  struct iovec {

 void   *iov_base;  //Base address.

 size_t iov_len;    // Length.

 };

 @endcode

  Each iovec entry specifies the base address and length of an area

 in memory from which data should be written.

 The writev system call

 will always write a complete area before proceeding

 to the next.

  On objects capable of seeking, the write starts at a position

 given by the pointer associated with fd ,

 see lseek .

 Upon return from write ,

 the pointer is incremented by the number of bytes which were written.

 If 'fd' refers to a shared memory object then write() on the shared memory object is supported by the current implementation.

  Objects that are not capable of seeking always write from the current

 position.

 The value of the pointer associated with such an object

 is undefined.

  When using non-blocking I/O on objects such as sockets that are subject

 to flow control, write and writev may write fewer bytes than requested;

 the return value must be noted,

 and the remainder of the operation should be retried when possible.

 Examples:

 @code

 /* Detailed description: This sample code creates an Example.txt file in the current working

  * directory(if file existes then it is truncated) and writes "Hello World" string

  * to the file.

  *

  * Preconditions: Example.txt if present, it should not be read-only.

  */

 int main()

 {

  int fd = 0 ;

  char Buf[] = "Hello World" ;

  fd = open("Example.txt" , O_CREAT | O_TRUNC | O_RDWR  ,0666) ;

  if(fd < 0 )

  {

     printf("Failed to open file Example.txt") ;

     return -1 ;

  }

  if(write(fd , Buf , sizeof(Buf)) < sizeof(Buf))

   {

     printf("Failed to write string %s to file" , Buf) ;

     return -1 ;

   }

   printf("String %s written to file 

 " , Buf) ;

   return 0 ;

  }

 @endcode

  Output

 @code

 String Hello World written to file

 @endcode

 @code

 /*

  * Detailed description  : Sample usage of readv system call

  */

 #include <stdio.h>

 #include <sys/types.h>

 #include <sys/uio.h>

 #include <fcntl.h>

 int main()

 {

   int fd = 0 ;

   struct iovec io_vec[1] ;

   char Buf[12] = "Hello world" ;

   io_vec[0].iov_base  = Buf ;

   io_vec[0].iov_len = 11 ;

   fd = open("Example.txt" , O_CREAT | O_RDWR , 0666 ) ;

   if(fd < 0 )  {

     printf("File open failed") ;

     return -1 ;

   }

   if(writev(fd , io_vec , 1) <  11 )   {

     printf("Failed to read fron Example.txt file") ;

     return -1 ;

   }

   printf("writev succes %s written"  , io_vec[0].iov_base) ;

   return 0 ; }

 @endcode

  Output

 @code

 writev succes Hello world written

 @endcode

 @see fcntl()

 @see lseek()

 @see open()

 @see pipe()

 @see select()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  confstr(int name, char *buf, size_t len)

 @param name

 @param buf

 @param len

 @return   If the call to confstr is not successful, 0 is returned and errno is set appropriately.

 Otherwise, if the variable does not have a configuration defined value,

 0 is returned and errno is not modified.

 Otherwise, the buffer size needed to hold the entire configuration-defined

 value is returned.

 If this size is greater than the argument len, the string in buf was truncated.

   The confstr function provides a method for applications to get configuration

 defined string values.

 The name argument specifies the system variable to be queried. Symbolic 

   constants for each name value are found in the include file \#include \<unistd.h.\> The len argument specifies the size of the buffer referenced by the argument buf. If len is non-zero, buf is a non-null pointer, and name has a value, up to len - 1 bytes of the value are copied into the buffer buf. The copied value is always null terminated.

  The available values are as follows:

 @code

  _CS_PATH

   Return a value for the PATH environment variable that finds all the standard utilities.

 @endcode

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 #include <stdlib.h>

 int main()

 {

  int n = 0;

  char *buf = NULL;

  int len = 0;

  n = confstr(_CS_PATH, NULL, 0);

  printf("{Expected: 31} %d", n);

  if( n == 0 )

     return -1;

  buf = (char *)malloc(n);

  if ( buf == NULL )

  {

     printf("malloc failed!!");

     return -1;

  }

  len = confstr(_CS_PATH, buf, n);

  printf("PATH in buffer: \n%s", buf);

  printf("length: %d", len);

  free(buf);

  return 0;

 }

 @endcode

  Output

 @code

 PATH in buffer:

 /usr/bin:/bin:/usr/sbin:/sbin:

 length: 31

 @endcode

 @see pathconf()

 @see sysconf()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn getopt(int nargc, char * const nargv[], const char *ostr)

 @param nargc

 @param nargv

 @param ostr

 @return The  getopt function returns the next known option character in  optstring. If  getopt encounters a character not found in  optstring or if it detects a missing option argument, it returns ‘?’ (question mark. If  optstring has a leading ‘:’ then a missing option argument causes ‘:’ to be returned instead of ‘?.’ In either case, the variable  optopt is set to the character that caused the error. The  getopt function returns -1 when the argument list is exhausted.

 The  getopt function incrementally parses a command line argument list  argv and returns the next  known option character. An option character is  known if it has been specified in the string of accepted option characters,  optstring.

 The option string optstring may contain the following elements: individual characters, and characters followed by a colon to indicate an option argument is to follow. For example, an option string x recognizes an option "-x", and an option string x: recognizes an option and argument "-x argument." It does not matter to getopt if a following argument has leading white space.

 On return from getopt, optarg points to an option argument, if it is anticipated, and the variable optind contains the index to the next argv argument for a subsequent call to getopt. The variable optopt saves the last known option character returned by getopt.

 The variables opterr and optind are both initialized to 1. The optind variable may be set to another value before a set of calls to getopt in order to skip over more or less argv entries.

 In order to use getopt to evaluate multiple sets of arguments, or to evaluate a single set of arguments multiple times, the variable optreset must be set to 1 before the second and each additional set of calls to getopt, and the variable optind must be reinitialized.

 The getopt function returns -1 when the argument list is exhausted. The interpretation of options in the argument list may be cancelled by the option ‘--’ (double dash) which causes getopt to signal the end of argument processing and return -1. When all options have been processed (i.e., up to the first non-option argument), getopt returns -1. 

 Examples:

 @code

 #include <unistd.h>

 #include <stdio.h>

 #include <fcntl.h>

 #include <errno.h>

 #include <string.h>

 int main()

 {

         int argc = 3;

         char *argv[] =

          {

                  "getopt","-f","hi"

          };

         int bflag, ch, fd;

         bflag = 0;

         while ((ch = getopt(argc, argv, "bf:")) != -1) {

         switch (ch) {

         case 'b':

                 bflag = 1;

                 printf("option is 'b' \n");

                 break;

         case 'f':

                 printf("option is 'f' \n");

                 if ((fd = open(optarg, O_RDONLY, 0)) != 0) {

                         (void)fprintf(stderr,

                            "myname: %s: %s\n", optarg, strerror(errno));                

                 }                             

                 break;

         case '?':

                 printf("missing option!");

         default:

                 printf("unknown option!");

         }

 }

 argc -= optind;

 return 0;

 }

 @endcode

  Output

 @code

 option is ’f’

 myname: hi: No such file or directory

 @endcode

 @see getopt_long()

 Bugs:

 The  getopt function was once specified to return  EOF instead of -1. This was changed by  -p1003.2-92 to decouple  getopt from

  	\#include \<stdio.h\>

 A single dash "-" may be specified as a character in optstring, however it should never have an argument associated with it. This allows getopt to be used with programs that expect "-" as an option flag. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility only. Care should be taken not to use ‘-’ as the first character in optstring to avoid a semantic conflict with GNU getopt, which assigns different meaning to an optstring that begins with a ‘-.’ By default, a single dash causes getopt to return -1.

 It is also possible to handle digits as option letters. This allows getopt to be used with programs that expect a number ("-3") as an option. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility only. The following code fragment works in most cases.

 @code

 int ch;

 long length;

 char *p, *ep;

 while ((ch = getopt(argc, argv, "0123456789")) != -1)

         switch (ch) {

         case ’0’: case ’1’: case ’2’: case ’3’: case ’4’:

         case ’5’: case ’6’: case ’7’: case ’8’: case ’9’:

                 p = argv[optind - 1];

                 if (p[0] == ’-’ Am]Am] p[1] == ch Am]Am] !p[2]) {

                         length = ch - ’0’;

                         ep = "";

                 } else if (argv[optind] Am]Am] argv[optind][1] == ch) {

                         length = strtol((p = argv[optind] + 1),

                             Am]ep, 10);

                         optind++;

                         optreset = 1;

                 } else

                         usage();

                 if (*ep != ’\0’)

                         errx(EX_USAGE, "illegal number -- %s", p);

                 break;

         }

 @endcode

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  fsync(int fd)

 @param fd

 @return   Upon successful completion, fsync() returns 0. Otherwise, it returns -1 and sets 

 errno to indicate the error. If the fsync() function fails, outstanding I/O operations 

 are not guaranteed to have been completed.

   The fsync system call

 causes all modified data and attributes of fd to be moved to a permanent storage device.

 This normally results in all in-core modified copies

 of buffers for the associated file to be written to a disk.

  The fsync system call should be used by programs that require a file to 

   be in a known state, for example, when building a simple transaction facility.

 Examples:

 @code

 /*

  * Detailed description : Simple usage of fsync system call.

  * Preconditions : Example.txt if present should not a ready-only file

  */

 #include <unistd.h>

 #include <fcntl.h>

 int main()

 {

   int fd = 0;

   fd = open("Example.txt" , O_CREAT | O_RDWR , 0666);

   if(fd < 0 )  

   {

      printf("Failed to open file Example.txt");

      return -1;

   }

   if(fsync(fd) < 0 )  

   {

      printf("fsync system call failed");

      return -1;

   }

   close(fd);

   printf("fsync system call succeeded");

   return 0;

 }

 @endcode

  Output

 @code

 fsync system call succeeded

 @endcode

 @see fsync()

 @see sync()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  fdatasync(int filedesc)

 @param filedesc

 @return   If successful the function returns 0, otherwise it returns (-1) and sets errno 

   to indicate the error.

   The fdatasync system call

 causes all modified data and attributes of fd to be moved to a permanent storage device.

 This normally results in all in-core modified copies

 of buffers for the associated file to be written to a disk.

 The fdatasync() function forces all the queued I/O operations associated that

 file, as indicated by the file descriptor fd, to the synchronized I/O completion

 state.

  The functionality shall be equivalent to fsync() with the symbol _POSIX_SYNCHRONIZED_IO 

   defined. This has an exception that all I/O operations shall be completed before 

   the call.

  The fdatasync should be used by programs that require a file to be in 

   a known state, for example when building a simple transaction facility.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 #define KMAXCHARS 100

 int test_fdatasync()

 {

    char* array = "abcdefghijklmnopqrstuvwxyz";

    struct stat buf;

    if((fd = open(file , O_CREAT | O_RDWR , 0666))  < 0)

    {

       printf("Failed  to create file");

    }

    size_t size = write(fd,array, KMAXCHARS);

    if(fdatasync(fd) < 0)

    {

      printf("Fdatasync failed");

      int retrn = remove(file);

      return -1;

    }

   int retVal2 = fstat( fp, &buf; );

   if(!retVal2)

   {

     size_t bufsize = buf.st_size;

     if (bufsize == size)

     {

       printf("file size = %d", size);

       printf("Fdatasync passed");

       int retrn = remove(file);

       return 0;

     }

   }

 }

 @endcode

  Output

 @code

 file size = 50

 Fdatasync passed

 @endcode

 @see sync()

 @see fsync()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn ftruncate(int filedesc, off_t length)

 @param filedesc

 @param length

 Refer to truncate() for documentation

 @see open()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn ftruncate64(int filedesc, off64_t length)

 @param filedesc

 @param length

 For full documentation see: http://www.unix.org/version2/whatsnew/lfs20mar.html#3.0

 @see ftruncate()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  readlink(const char *path, char *buf, int bufsize)

 @param path

 @param buf

 @param bufsize

 @return   The call returns the count of characters placed in the buffer

 if it succeeds, or a -1 if an error occurs, placing the error

 code in the global variable errno.

   The readlink system call

 places the contents of the symbolic link path in the buffer buf, which has size bufsize. The readlink system call does not append a NULL character to buf.

 Examples:

 @code

 /*

 * Detailed description: Example to read a link file

 * Precondition: "Parent.txt" should exist in c: drive with some contents

 *                of length atleast 25 characters.  And a link file by name           

 *                "C:\Link" pointing to parent file should exist.

 *

 */

 #include <unistd.h>

 #include <stdio.h>

 int main(void)

 {

     char rdbuff[25];

     int retval;

    if((retval = (readlink("C:\Link", rdbuff, (sizeof(char)*25)))) < 0)

     {

        printf("Read through link file failed");

        perror(" ");

        return -1;

     }

     printf("Read through link file succeeded");

 }

 @endcode

  Output

 @code

 Read through link file succeeded.

 @endcode

 Limitations:

 The path parameter of the readlink() function should not exceed 256 characters in length. 

 @see lstat()

 @see stat()

 @see symlink()

 @see symlink()

 @capability Deferred @ref RFs::Entry(const TDesC16&, TEntry&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn gethostname(char *name, size_t size)

 @param name

 @param size

 @return On successful completion, 0 is returned. Otherwise, -1 is returned

 The gethostname() function returns the standard host name for the current machine. The size argument specifies the size of the array pointed to by the name argument. The returned name is null-terminated, except that if size is an insufficient length to hold the host name, then the returned name is truncated and it is unspecified whether the returned name is null-terminated. 

 Host names are limited to 255 bytes

 @see uname()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setegid(gid_t gid)

 @param gid

 Refer to  setuid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  seteuid(uid_t uid)

 @param uid

 Refer to  setuid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  symlink(const char *oldpath, const char *newpath)

 @param oldpath

 @param newpath

 @return   Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno set to indicate the error.

  A symbolic link newpath is created to oldpath (newpath is the name of the file created, oldpath is the string used in creating the symbolic link). Either name 

   may be an arbitrary path name. 

  The creation time stamp is not supported, only access and modification time 

   stamps. Creating a link in a directory will not alter the time stamps of the 

   directory itself.

 Examples:

 @code

 /*

 * Detailed description  : Example to create symlink to a file.

 * Precondition : "Parent.txt" should exist in c: drive.

 * Remarks      : Symlink behaviour is exactly similar to link api.

 */

 #include <unistd.h>

 #include <stdio.h>

 int main(void)

  {

     if(symlink("C:\Parent.txt","C:\Link") < 0)

     {

          printf("simulated link creation to parent file failed");

          return -1  ;

     }

     printf("simulated link to parent file created");

     return 0 ;

  }

 @endcode

  Output

 @code

 simulated link to parent file created.

 @endcode

 Limitations:

 - The oldpath and newpath parameters of the symlink() function should not exceed 256 characters in length. 

 - P.I.P.S. does not support links across file systems.

 - P.I.P.S. does not support symlink on directories or existing link files.

 - P.I.P.S. only simulates link files and does not distinguish between hard and symbolic links so link() and symlink() on P.I.P.S. are identical.

 - KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive

 not found or filesystem not mounted on the drive.

 @see link()

 @see lstat()

 @see readlink()

 @see unlink()

 @see symlink()

 @capability Deferred @ref RFs::Delete(const TDesC16&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  fchdir(int filedesc)

 @param filedesc

 Refer to  chdir() for the documentation

 @capability Deferred @ref RFs::SetSessionPath(const TDesC16&)

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getpgid(pid_t pid)

 @param pid

 Refer to  getpgrp() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  lchown(const char *path, uid_t owner, gid_t group)

 @param path

 @param owner

 @param group

 Refer to  chown() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  nice(int incr)

 @param incr

  The nice function obtains the scheduling priority of the process from 

   the system and sets it to the priority value specified in incr. The priority is a value in the range -20 to 20. The default priority 

   is 0. Lower priorities cause more favorable scheduling.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 int test_nice()

 {

    int retVal;

    errno = 0;

    int i = -10;

    int ret_get1 = getpriority(PRIO_PROCESS,0);

    retVal = nice(i);

    int ret_get2 = getpriority(PRIO_PROCESS,0);

    if((retVal == -1)&&(errno))

    {

       printf("failed");

       return -1;

    }

    else

    {

      if(!(i - (ret_get2 - retget1)))

      printf("Nice value: %d", i)

      printf("nice passed");

    }

    return 0;

 }       

 @endcode

  Output

 @code

 Nice value: -10

 nice passed

 @endcode

 @see getpriority()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setpgrp(pid_t _pid, pid_t _pgrp)

 @param _pid

 @param _pgrp

 Refer to  setpgid() for the documentation

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setregid(gid_t rgid, gid_t egid)

 @param rgid

 @param egid

 @return   These functions always return 0.

   These functions are build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  setreuid(uid_t ruid, uid_t euid)

 @param ruid

 @param euid

 @return   These functions always return 0.

   These functions are build supported but not available functionally. Symbian 

 OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn swab(const void *from, void *to, ssize_t len)

 @param from

 @param to

 @param len

 The function  swab copies  len bytes from the location referenced by  from to the location referenced by  to, swapping adjacent bytes.

 The argument len must be an even number.

 Examples

 @code

 #include <string.h>

 #include <stdio.h>

 int main()

 {

     int i=0x00003366,j=0x0;

     swab((void *)&i,(void *)&j,2);

     if(j==0x6633)

        printf("Ouput val = %#x\n",j);

     return 0;

 }

 @endcode

 output

 @code

 Ouput val = 0x6633

 @endcode

 @see bzero()

 @see memset()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  usleep(useconds_t microseconds)

 @param microseconds

 @return   The usleep function returns the value 0 if successful; otherwise the value -1 is

 returned and the global variable errno is set to indicate the error.

   The usleep function suspends execution of the calling process until either microseconds microseconds have elapsed or a signal is delivered to the process and its

 action is to invoke a signal-catching function or to terminate the

 process.

 System activity may lengthen the sleep by an indeterminate amount.

  This function is implemented using nanosleep by pausing for microseconds microseconds or until a signal occurs.

 Consequently, in this implementation,

 sleeping has no effect on the state of process timers,

 and there is no special handling for SIGALRM.

 Limitations:

 The signal related functionaities aren’t applicable to the symbian implementation as there is no support for signals from symbian.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 int main()

 {

  unsigned long t = 2; 

  int i;

  i = usleep(t);

  printf("Expected: 0 usleep returned: %d", i);

  return 0;

 }

 @endcode

  Output

 @code

 Expected: 0 usleep returned: 0

 @endcode

 @see nanosleep()

 @see sleep()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn truncate(const char *file, off_t length)

 @param file

 @param length

 @return   Upon successful completion, both truncate() and ftruncate() shall return 0; otherwise, -1 shall be returned and errno set to indicate the error.

 The  truncate system call causes the file named by  file or referenced by  filedesc to be truncated to  length bytes in size. If the file was larger than this size, the extra data is lost. If the file was smaller than this size, it will be extended as if by writing bytes with the value zero. With  ftruncate, the file must be open for writing.

 Examples:

 @code

 //example for truncate

 #include<unistd.h>

 #include<stdio.h>

 #include <sys/stat.h>

 int test_truncate()

 {

         int retVal, retVal2, retSize, retSize2;

         struct stat buf;

         ssize_t size;

         char *buffer = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx";

         int fp = open("c:\test.txt", O_RDWR|O_CREAT);

         size = write(fp,buffer,50);

         close(fp);

         retVal2 = stat("c:\test.txt", &buf );

         if ( !retVal2 )

         {

         retSize = buf.st_size;

         printf("Size before: %d", retSize);

         retVal = truncate("c:\test.txt", retSize/2 );

         }

         else

         {

         printf("Failed");

         }

         retVal2 = stat( "c:\test.txt", &buf );

         if ( !retVal2 )

                 {

                 retSize2 = buf.st_size;

                 if( retSize2 == (retSize/2 ) )

                         {

                         printf("\nSize after: %d\n", retSize2);

                         printf("Truncate passed");

                         return 0;

                         }

                 else

                         {

                         printf("Failed");

                         return -1;

                         }

                 }

         else

                 {

                 printf("Failed");

                 return -1;

                 }

 }

 @endcode

  Output

 @code

 Size before: 50

 Size after: 25

 Ttruncate Passed

 @endcode

 Errors:

 The truncate and ftruncate succeed unless:

 [EBADF] The filedesc argument is not a valid descriptor for a regular file.

 [EINVAL] The filedesc argument references to an object other than a file. 

 [EINVAL] The filedesc descriptor is not open for writing.

 Bugs:

 These calls should be generalized to allow ranges of bytes in a file to be discarded.

 Use of truncate to extend a file is not portable. 

 @see open()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn truncate64(const char *file, off64_t length)

 @param file

 @param length

 @return   Upon successful completion, both truncate64() and ftruncate64() shall return 0; otherwise, -1 shall be returned and errno set to indicate the error.

 For full documentation see: http://www.unix.org/version2/whatsnew/lfs20mar.html#3.0

 @see truncate()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  brk(const void*)

 @return   Function always returns 0.

   The brk function is used to change the amount of memory allocated in a

 process's data segment.It does this by moving the location of the "break".

 This functionality is not supported by the Symbian OS platform and hence

 is only build supported.

 @see mmap()

 @see free()

 @see malloc()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getdtablesize(void)

 @return  

   Each process has a fixed size descriptor table,

 which is guaranteed to have at least 20 slots.

 The entries in

 the descriptor table are numbered with small integers starting at 0.

 The getdtablesize system call returns the size of this table.

 Examples:

 @code

 #include <stdio.h>

 int main()

 {

         printf("maximum number of files that can be opened by a process is %d",getdtablesize());

 }

 @endcode

  Output

 @code

 maximum number of files that can be opened by a process is 1024

 @endcode

 @see close()

 @see dup()

 @see open()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  getpagesize(void)

   The getpagesize function

 returns the number of bytes in a page.

 Page granularity is the granularity of many of the memory

 management calls.

  The page size is a system

 page size and may not be the same as the underlying

 hardware page size.

 Examples:

 @code

 #include<unistd.h>

 #include<stdio.h>

 int test_getpagesize()

 {

    int retVal = 0;

    retVal = getpagesize();

    if( retVal >= 0)

    {

       printf("getpagesize passed");

       printf("

  retVal  = %d " retVal);

       return retVal;

    }

    else

    {

    printf("Failed");

    return -1;

    }

 }       

 @endcode

  Output

 @code

 getpagesize passed

 retVal = 4096

 @endcode

 @see sbrk()

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn  initgroups(const char *, gid_t)

 @return   These functions always return 0.

  The getgroups function is build supported but not available functionally. 

   Symbian OS does not support multiple users and groups.

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn issetugid(void)

 @return  The issetugid() function returns 1 if the process  was  made setuid  or  setgid  as  the result of the last or a previous call to execve(). Otherwise it returns 0

 The issetugid() function enables library functions (in  lib-termlib,   libc,  or  other  libraries)  to  guarantee  safe behavior when  used  in  setuid  or  setgid  programs.  Some library  functions  might be passed insufficient informationand not know whether the current program was started  setuidor  setgid  because  a  higher level calling code might have made changes to the uid, euid, gid, or egid. These low-levellibrary  functions are therefore unable to determine if theyare being run with elevated or normal privileges.

 Errors:

 The issetugid() function is  always  successful.  No  return value is reserved to indicate an error.

 g

 @publishedAll

 @externallyDefinedApi

 */

 /** @fn mkstemp(char *template)

 @param template