Open System Services System Calls Reference Manual (G06.25+, H06.03+)

chmod(2) OSS System Calls Reference Manual
NAME
chmod - Changes file access permissions
LIBRARY
G-series native Guardian processes: system library
G-series native OSS processes: system library
H-series native Guardian processes: implicit libraries
H-series OSS processes: implicit libraries
SYNOPSIS
#include <sys/types.h> /* optional except for POSIX.1 */
#include <sys/stat.h>
int chmod(
const char *path,
mode_t mode);
PARAMETERS
path Specifies the full pathname of the file. If the path parameter refers to a symbolic
link, the chmod() function changes access permissions on the file specified by
the symbolic link.
mode Specifies the bit pattern that determines the access permissions.
DESCRIPTION
The chmod() function sets the access permissions of the file specified by the path parameter
according to the bit pattern specified by the mode parameter.
To change file-access permissions, either the process must have appropriate privileges or its
effective user ID must be the same as the user ID of the file owner.
If the S_ISVTX bit is on for a directory, only processes with an effective user ID equal to the
user ID of the file’s owner or the directory’s owner, or a process with appropriate privileges, can
remove files from the directory.
A call to the chmod() function has no effect on the file descriptor for a file that is open at the
time of the call. However, new openers of the file will be authorized by using the new access per-
missions that were specified in the call.
The mode parameter is constructed by logically ORing one or more of these symbols, which are
defined in the sys/stat.h header file:
S_ISUID Sets the process’s effective user ID to the user ID of the file’s owner on execu-
tion.
S_ISGID Sets the process’s effective group ID to the group ID of the file’s group on execu-
tion.
S_ISVTX For a directory, permits modification to the directory only if the effective user ID
of the process matches that of the file being accessed.
S_IRWXU Permits the file’s owner to read, write, and execute the file (or to search the direc-
tory).
S_IRUSR Permits the file’s owner to read the file.
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