fchmod

fchmod

Change Directory or File Mode

Portability: POSIX.1 conforming

SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h>

int fchmod(int fileDescriptor, mode_t mode);

DESCRIPTION

fchmod changes the file permission flags for the directory or file specified by fileDescriptor . The mode argument can be any combination of the following symbols, which are defined in <stat.h> :

S_ISUID sets the user ID for execution. When the specified file is processed through an exec function, the user ID of the process is also set for execution.

S_ISGID sets group ID for execution. When the specified file is processed through an exec function, the group ID of the process is also set for execution.

S_ISVTX specifies shared text.

S_IRUSR sets file owner permission to read.

S_IWUSR sets file owner permission to write.

S_IXUSR sets file owner permission to execute.

S_IRWXU sets file owner permission to read, write, and execute.

S_IRGRP sets group permission to read.

S_IWGRP sets group permission to write.

S_IXGRP sets group permission to execute.

S_IRWXG sets group permission to read, write, and execute.

S_IROTH sets general permission to read.

S_IWOTH sets general permission to write.

S_IXOTH sets general permission to execute.

S_IRWXO sets general permission to read, write, and execute.

RETURN VALUE

fchmod returns 0 if it is successful. If unsuccessful, a -1 is returned.

EXAMPLE

This example changes a file whose file number is passed so that it can be executed by any user who can read it:

#include <sys/types.h>
#include <sys/stat.h>

int fchexec(int fd) {
   struct stat stat_data;
   mode_t newmode;
   int rc;

   rc = fstat(fd, &stat_data);
   if (rc != 0) {
      perror("fstat failure");
      return -1;
   }
   newmode = stat_data.st_mode;
   if (newmode & S_IRUSR) newmode |= S_IXUSR;
   if (newmode & S_IRGRP) newmode |= S_IXGRP;
   if (newmode & S_IROTH) newmode |= S_IXOTH;

      /* If the mode bits changed, make them effective. */
   if (newmode != stat_data.st_mode) {  
      rc = fchmod(fd, newmode);         
      if (rc != 0) perror("fchmod failure");
      return rc;
   }
   return(0);    /* No change was necessary.            */
}

RELATED FUNCTIONS

chmod , chown

SEE ALSO

Chapter 19, "Introduction to POSIX," in SAS/C Library Reference, Volume 2
File Management Functions

Chapter Contents
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`S_ISUID`	sets the user ID for execution. When the specified file is processed through an `exec` function, the user ID of the process is also set for execution.
`S_ISGID`	sets group ID for execution. When the specified file is processed through an `exec` function, the group ID of the process is also set for execution.
`S_ISVTX`	specifies shared text.
`S_IRUSR`	sets file owner permission to read.
`S_IWUSR`	sets file owner permission to write.
`S_IXUSR`	sets file owner permission to execute.
`S_IRWXU`	sets file owner permission to read, write, and execute.
`S_IRGRP`	sets group permission to read.
`S_IWGRP`	sets group permission to write.
`S_IXGRP`	sets group permission to execute.
`S_IRWXG`	sets group permission to read, write, and execute.
`S_IROTH`	sets general permission to read.
`S_IWOTH`	sets general permission to write.
`S_IXOTH`	sets general permission to execute.
`S_IRWXO`	sets general permission to read, write, and execute.