Open System Services System Calls Reference Manual (G06.28+, H06.05+)

fchmod(2) OSS System Calls Reference Manual
NAME
fchmod - 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 fchmod(
int filedes,
mode_t mode);
PARAMETERS
filedes Specifies the file descriptor of an open file.
mode Specifies the bit pattern that determines the access permissions.
DESCRIPTION
The fchmod( ) function sets the access permissions of a file pointed to by the filedes parameter
according to the bit pattern specified by the mode parameter. The fchmod( ) function is like the
chmod() function except that it operates on a file descriptor instead of a pathname.
To change the file access permissions of a file or directory, the effective user ID of the process |
must match the super ID or the owner of the file, or its effective user ID or one of its group |
affiliations must qualify it for membership in the Safeguard SECURITY-OSS- |
ADMINISTRATOR group. |
If fchmod() is invoked by a process whose effective user ID does not equal the super ID or file |
owner, the set-user-ID and set-group-ID bits of the file mode (04000 and 02000, respectively) are |
cleared.
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 fchmod() 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.
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