readlink()

Place the contents of a symbolic link into a buffer

Synopsis:

#include <unistd.h>

int readlink( const char* path, 
              char* buf, 
              size_t bufsiz );

Arguments:

path: The name of the symbolic link.
buf: A pointer to a buffer where the function can store the contents of the symbolic link (i.e. the path linked to).
bufsiz: The size of the buffer.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

The readlink() function places the contents of the symbolic link named by path into the buffer pointed to by buf, which has a size of bufsiz. The contents of the returned symbolic link doesn't include a NULL terminator. Its length must be determined from the stat structure returned by lstat(), or by the return value of the readlink() call.

If readlink() is successful, up to bufsiz bytes from the contents of the symbolic link are placed in buf.

Returns:

The number of bytes placed in the buffer, or -1 if an error occurs (errno is set).

Errors:

EACCES: Search permission is denied for a component of the path prefix.
EINVAL: The named file isn't a symbolic link.
ELOOP: A loop exists in the symbolic links encountered during resolution of the path argument, and more than SYMLOOP_MAX symbolic links were encountered.
ENAMETOOLONG: A component of the path exceeded NAME_MAX characters, or the entire pathname exceeded PATH_MAX characters.
ENOENT: The named file doesn't exist.
ENOSYS: Links aren't supported by the resource manager associated with path.
ENOTDIR: A component of the path prefix named by path isn't a directory.

Examples:

/*
 * Read the contents of the named symbolic links
 */
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

char buf[PATH_MAX + 1];

int main( int argc, char** argv )
{
  int n;
  int len;
  int ecode = 0;

  for( n = 1; n < argc; ++n ) {
    if(( len = readlink( argv[n], buf, PATH_MAX )) == -1) {
      perror( argv[n] );
      ecode++;
    }
    else {
      buf[len] = '\0';
      printf( "%s -> %s\n", argv[n], buf );
    }
  }

  return( ecode );
}

Classification:

POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes