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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] .TH CHMOD 2 "Mar 2, 2021" .SH NAME chmod, fchmod, fchmodat \- change access permission mode of file .SH SYNOPSIS .LP .nf #include #include \fBint\fR \fBchmod\fR(\fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR); .fi .LP .nf \fBint\fR \fBfchmod\fR(\fBint\fR \fIfildes\fR, \fBmode_t\fR \fImode\fR); .fi .LP .nf \fBint\fR \fBfchmodat\fR(\fBint\fR \fIfildes\fR, \fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR, \fBint\fR \fIflag\fR); .fi .SH DESCRIPTION .LP The \fBchmod()\fR, \fBfchmod()\fR, and \fBfchmodat()\fR functions set the access permission portion of the mode of the file whose name is given by \fIpath\fR or referenced by the open file descriptor \fIfildes\fR to the bit pattern contained in \fImode\fR. Access permission bits are interpreted as follows: .sp .sp .TS l l l l l l . \fBS_ISUID\fR 04000 Set user ID on execution. \fBS_ISGID\fR 020#0 T{ Set group ID on execution if # is \fB7\fR, \fB5\fR, \fB3\fR, or \fB1\fR. Enable mandatory file/record locking if # is \fB6\fR, \fB4\fR, \fB2\fR, or \fB0\fR. T} \fBS_ISVTX\fR 01000 Sticky bit. \fBS_IRWXU\fR 00700 Read, write, execute by owner. \fBS_IRUSR\fR 00400 Read by owner. \fBS_IWUSR\fR 00200 Write by owner. \fBS_IXUSR\fR 00100 T{ Execute (search if a directory) by owner. T} \fBS_IRWXG\fR 00070 Read, write, execute by group. \fBS_IRGRP\fR 00040 Read by group. \fBS_IWGRP\fR 00020 Write by group. \fBS_IXGRP\fR 00010 Execute by group. \fBS_IRWXO\fR 00007 Read, write, execute (search) by others. \fBS_IROTH\fR 00004 Read by others. \fBS_IWOTH\fR 00002 Write by others. \fBS_IXOTH\fR 00001 Execute by others. .TE .sp .LP Modes are constructed by the bitwise OR operation of the access permission bits. .sp .LP The effective user ID of the process must match the owner of the file or the process must have the appropriate privilege to change the mode of a file. .sp .LP If the process is not a privileged process and the file is not a directory, mode bit 01000 (save text image on execution) is cleared. .sp .LP If neither the process is privileged nor the file's group is a member of the process's supplementary group list, and the effective group ID of the process does not match the group ID of the file, mode bit 02000 (set group ID on execution) is cleared. .sp .LP If a directory is writable and has \fBS_ISVTX\fR (the sticky bit) set, files within that directory can be removed or renamed only if one or more of the following is true (see \fBunlink\fR(2) and \fBrename\fR(2)): .RS +4 .TP .ie t \(bu .el o the user owns the file .RE .RS +4 .TP .ie t \(bu .el o the user owns the directory .RE .RS +4 .TP .ie t \(bu .el o the file is writable by the user .RE .RS +4 .TP .ie t \(bu .el o the user is a privileged user .RE .sp .LP If a regular file is not executable and has \fBS_ISVTX\fR set, the file is assumed to be a swap file. In this case, the system's page cache will not be used to hold the file's data. If the \fBS_ISVTX\fR bit is set on any other file, the results are unspecified. .sp .LP If a directory has the set group ID bit set, a given file created within that directory will have the same group ID as the directory. Otherwise, the newly created file's group ID will be set to the effective group ID of the creating process. .sp .LP If the mode bit 02000 (set group ID on execution) is set and the mode bit 00010 (execute or search by group) is not set, mandatory file/record locking will exist on a regular file, possibly affecting future calls to \fBopen\fR(2), \fBcreat\fR(2), \fBread\fR(2), and \fBwrite\fR(2) on this file. .sp .LP If \fIfildes\fR references a shared memory object, \fBfchmod()\fR need only affect the \fBS_IRUSR\fR, \fBS_IRGRP\fR, \fBS_IROTH\fR, \fBS_IWUSR\fR, \fBS_IWGRP\fR, \fBS_IWOTH\fR, \fBS_IXUSR\fR, \fBS_IXGRP\fR, and \fBS_IXOTH\fR file permission bits. .sp .LP If \fIfildes\fR refers to a socket, \fBfchmod()\fR does not fail but no action is taken. .sp .LP If \fIfildes\fR refers to a stream that is attached to an object in the file system name space with \fBfattach\fR(3C), the \fBfchmod()\fR call performs no action and returns successfully. .sp .LP The \fBfchmodat()\fR function behaves similarly to \fBchmod()\fR, except when \fIpath\fR is a relative path, it is resolved relative to the directory specified by \fIfiledes\fR. If \fBfiledes\fR has the value \fBAT_FDCWD\fR, then \fBpath\fR will be resolved relative to the current working directory. The argument \fIflag\fR should be zero, but may include the value \fBAT_SYMLINK_NOFOLLOW\fR, which indicates that if \fIpath\fR refers to a symbolic link, then permissions should be changed on the symbolic link itself. However, changing permissions of symbolic links is not supported on illumos, and will result in an error. .sp .LP Upon successful completion, \fBchmod()\fR, \fBfchmod()\fR, \fBfchmodat()\fR mark for update the \fBst_ctime\fR field of the file. .SH RETURN VALUES .LP Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is returned, the file mode is unchanged, and \fBerrno\fR is set to indicate the error. .SH ERRORS .LP The \fBchmod()\fR, \fBfchmod()\fR, and \fBfchmodat()\fR functions will fail if: .sp .ne 2 .na \fB\fBEIO\fR\fR .ad .RS 9n An I/O error occurred while reading from or writing to the file system. .RE .sp .ne 2 .na \fB\fBEPERM\fR\fR .ad .RS 9n The effective user ID does not match the owner of the file and the process does not have appropriate privilege. .sp The {\fBPRIV_FILE_OWNER\fR} privilege overrides constraints on ownership when changing permissions on a file. .sp The {\fBPRIV_FILE_SETID\fR} privilege overrides constraints on ownership when adding the setuid or setgid bits to an executable file or a directory. When adding the setuid bit to a root owned executable, additional restrictions apply. See \fBprivileges\fR(5). .RE .sp .LP The \fBchmod()\fR and \fBfchmodat()\fR functions will fail if: .sp .ne 2 .na \fB\fBEACCES\fR\fR .ad .RS 16n Search permission is denied on a component of the path prefix of \fIpath\fR and for \fBfchmodat()\fR, \fBfiledes\fR was not opened with \fBO_SEARCH\fR requsted. The privilege {\fBFILE_DAC_SEARCH\fR} overrides file permissions restrictions in that case. .RE .sp .ne 2 .na \fB\fBEFAULT\fR\fR .ad .RS 16n The \fIpath\fR argument points to an illegal address. .RE .sp .ne 2 .na \fB\fBELOOP\fR\fR .ad .RS 16n A loop exists in symbolic links encountered during the resolution of the \fIpath\fR argument. .RE .sp .ne 2 .na \fB\fBENAMETOOLONG\fR\fR .ad .RS 16n The length of the \fIpath\fR argument exceeds \fBPATH_MAX\fR, or the length of a \fIpath\fR component exceeds \fBNAME_MAX\fR while \fB_POSIX_NO_TRUNC\fR is in effect. .RE .sp .ne 2 .na \fB\fBENOENT\fR\fR .ad .RS 16n Either a component of the path prefix or the file referred to by \fIpath\fR does not exist or is a null pathname. .RE .sp .ne 2 .na \fB\fBENOLINK\fR\fR .ad .RS 16n The \fIfildes\fR argument points to a remote machine and the link to that machine is no longer active. .RE .sp .ne 2 .na \fB\fBENOTDIR\fR\fR .ad .RS 16n A component of the prefix of \fIpath\fR is not a directory. .RE .sp .ne 2 .na \fB\fBEROFS\fR\fR .ad .RS 16n The file referred to by \fIpath\fR resides on a read-only file system. .RE .sp .LP The \fBfchmod()\fR function will fail if: .sp .ne 2 .na \fB\fBEBADF\fR\fR .ad .RS 11n The \fIfildes\fR argument is not an open file descriptor .RE .sp .ne 2 .na \fB\fBENOLINK\fR\fR .ad .RS 11n The \fIpath\fR argument points to a remote machine and the link to that machine is no longer active. .RE .sp .ne 2 .na \fB\fBEROFS\fR\fR .ad .RS 11n The file referred to by \fIfildes\fR resides on a read-only file system. .RE .sp .LP The \fBchmod()\fR and \fBfchmod()\fR functions may fail if: .sp .ne 2 .na \fB\fBEINTR\fR\fR .ad .RS 10n A signal was caught during execution of the function. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The value of the \fImode\fR argument is invalid. .RE .sp .LP The \fBfchmodat()\fR will fail if: .sp .ne 2 .na .B EBADF .ad .RS 16n The argument \fIpath\fR is a relative path and \fIfiledes\fR is not an open file descriptor or the value \fBAT_FDCWD\fR. .RE .sp .ne 2 .na .B EINVAL .ad .RS 16n The argument \fIflags\fR has a non-zero value other than \fBAT_SYMLINK_NOFOLLOW\fR. .RE .sp .ne 2 .na .B ENOTDIR .ad .RS 16n The argument \fIpath\fR is a relative path and \fIfiledes\fR is a valid file descriptor which does not refer to a file. .RE .sp .ne 2 .na .B EOPNOTSUPP .ad .RS 16n The \fBAT_SYMLINK_NOFOLLOW\fR bit is set in the \fIflags\fR argument and \fIpath\fR refers to a symbolic link. .RE .sp .LP The \fBchmod()\fR and \fBfchmodat()\fR functions may fail if: .sp .ne 2 .na \fB\fBELOOP\fR\fR .ad .RS 16n More than {\fBSYMLOOP_MAX\fR} symbolic links were encountered during the resolution of the \fIpath\fR argument. .RE .sp .ne 2 .na \fB\fBENAMETOOLONG\fR\fR .ad .RS 16n As a result of encountering a symbolic link in resolution of the \fIpath\fR argument, the length of the substituted pathname strings exceeds {\fBPATH_MAX\fR}. .RE .sp .LP The \fBfchmod()\fR function may fail if: .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 10n The \fIfildes\fR argument refers to a pipe and the system disallows execution of this function on a pipe. .RE .SH EXAMPLES .LP \fBExample 1 \fRSet Read Permissions for User, Group, and Others .sp .LP The following example sets read permissions for the owner, group, and others. .sp .in +2 .nf #include const char *path; \&... chmod(path, S_IRUSR|S_IRGRP|S_IROTH); .fi .in -2 .LP \fBExample 2 \fRSet Read, Write, and Execute Permissions for the Owner Only .sp .LP The following example sets read, write, and execute permissions for the owner, and no permissions for group and others. .sp .in +2 .nf #include const char *path; \&... chmod(path, S_IRWXU); .fi .in -2 .LP \fBExample 3 \fRSet Different Permissions for Owner, Group, and Other .sp .LP The following example sets owner permissions for CHANGEFILE to read, write, and execute, group permissions to read and execute, and other permissions to read. .sp .in +2 .nf #include #define CHANGEFILE "/etc/myfile" \&... chmod(CHANGEFILE, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH); .fi .in -2 .LP \fBExample 4 \fRSet and Checking File Permissions .sp .LP The following example sets the file permission bits for a file named \fB/home/cnd/mod1\fR, then calls the \fBstat\fR(2) function to verify the permissions. .sp .in +2 .nf #include #include int status; struct stat buffer \&... chmod("home/cnd/mod1", S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH); status = stat("home/cnd/mod1", &buffer;); .fi .in -2 .SH USAGE .LP If \fBchmod()\fR or \fBfchmod()\fR is used to change the file group owner permissions on a file with non-trivial ACL entries, only the ACL mask is set to the new permissions and the group owner permission bits in the file's mode field (defined in \fBmknod\fR(2)) are unchanged. A non-trivial ACL entry is one whose meaning cannot be represented in the file's mode field alone. The new ACL mask permissions might change the effective permissions for additional users and groups that have ACL entries on the file. .SH ATTRIBUTES .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Standard _ MT-Level Async-Signal-Safe .TE .SH SEE ALSO .LP \fBchmod\fR(1), \fBchown\fR(2), \fBcreat\fR(2), \fBfcntl\fR(2), \fBmknod\fR(2), \fBopen\fR(2), \fBread\fR(2), \fBrename\fR(2), \fBstat\fR(2), \fBwrite\fR(2), \fBfattach\fR(3C), \fBmkfifo\fR(3C), \fBstat.h\fR(3HEAD), \fBattributes\fR(5), \fBprivileges\fR(5), \fBstandards\fR(5) .sp .LP \fIProgramming Interfaces Guide\fR