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'\" te .\" Portions Copyright (c) 2005, 2023, Oracle and/or its affiliates. .\" Copyright (c) 1989, AT&T. All rights reserved. .\" Copyright (c) 2001, the Institute of Electrical and Electronics Engineers, Inc. and The Open Group. All rights reserved. .\" Oracle gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at http://www.opengroup.org/bookstore/. .\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html. This notice shall appear on any product containing this material. .TH chmod 2 "30 Jan 2023" "Oracle Solaris 11.4" "System Calls" .SH NAME chmod, fchmod, fchmodat \- change access permission mode of file .SH SYNOPSIS .LP .nf #include <sys/stat.h> \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 \fIfd\fR, \fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR, \fBint\fR \fIflag\fR); .fi .SH DESCRIPTION .sp .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 .TS tab( ); lw(1.01i) lw(0.69i) lw(3.79i) . \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 .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 does not have the {\fBPRIV_SYS_CONFIG\fR} privilege, and the file is not a directory, mode bit 01000 (\fBS_ISVTX\fR, the sticky bit) 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 Upon successful completion, \fBchmod()\fR, \fBfchmod()\fR, and \fBfchmodat()\fR mark for update the \fBst_ctime\fR field of the file. .sp .LP The \fBfchmodat()\fR function is equivalent to \fBchmod()\fR except in the case where \fIpath\fR specifies a relative path. In this case the file to be changed is determined relative to the directory associated with the file descriptor \fIfd\fR instead of the current working directory. If the file descriptor was opened without \fBO_SEARCH\fR, the function checks whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the file descriptor was opened with \fBO_SEARCH\fR, the function does not perform the check. If \fBfchmodat()\fR is passed the special value \fBAT_FDCWD\fR in the \fIfd\fR parameter, the current working directory is used. .sp .LP Values for \fIflag\fR are constructed by a bitwise-inclusive OR of flags from the following list, defined in \fB<fcntl.h>\fR .sp .ne 2 .mk .na \fB\fBAT_SYMLINK_NOFOLLOW\fR\fR .ad .RS 23n .rt If \fIpath\fR names a symbolic link, then the mode of the symbolic link is changed. .RE .sp .LP If \fIflag\fR is 0, the behavior shall be identical to a call to \fBchmod()\fR. .SH RETURN VALUES .sp .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 .sp .LP The \fBchmod()\fR, \fBfchmod()\fR, and \fBfchmodat()\fR functions will fail if: .sp .ne 2 .mk .na \fB\fBEPERM\fR\fR .ad .RS 9n .rt 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 \fBsetuid\fR bit to a root owned executable, additional restrictions apply. See \fBprivileges\fR(7). .sp The file has the \fBimmutable\fR system attribute set. .sp The file has the \fBrtime\fR system attribute set, but does not have the \fBappendonly\fR system attribute set. .sp The file has both the \fBrtime\fR and the \fBappendonly\fR system attributes set, and the \fImode\fR argument specifies changes to bits other than the write permission bits. .sp The file has both the \fBrtime\fR and the \fBappendonly\fR system attributes set, has a size greater than zero bytes, and the \fImode\fR argument specifies changes to bits other than removing the write permission bits. .RE .sp .ne 2 .mk .na \fB\fBEROFS\fR\fR .ad .RS 9n .rt The file referred to by \fIpath\fR resides on a read-only file system. .RE .sp .LP The \fBchmod()\fR and \fBfchmod()\fR functions will fail if: .sp .ne 2 .mk .na \fB\fBEIO\fR\fR .ad .RS 7n .rt An I/O error occurred while reading from or writing to the file system. .RE .sp .LP The \fBchmod()\fR and \fBfchmodat()\fR functions will fail if: .sp .ne 2 .mk .na \fB\fBEACCES\fR\fR .ad .RS 16n .rt Search permission is denied on a component of the path prefix of \fIpath\fR. The privilege {\fBFILE_DAC_SEARCH\fR} overrides file permissions restrictions in that case. .RE .sp .ne 2 .mk .na \fB\fBELOOP\fR\fR .ad .RS 16n .rt A loop exists in symbolic links encountered during the resolution of the \fIpath\fR argument. .RE .sp .ne 2 .mk .na \fB\fBENAMETOOLONG\fR\fR .ad .RS 16n .rt 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 .mk .na \fB\fBENOENT\fR\fR .ad .RS 16n .rt 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 .mk .na \fB\fBENOTDIR\fR\fR .ad .RS 16n .rt A component of the prefix of \fIpath\fR is not a directory. .RE .sp .LP The \fBchmod()\fR function will fail if: .sp .ne 2 .mk .na \fB\fBEFAULT\fR\fR .ad .RS 11n .rt The \fIpath\fR argument points to an illegal address. .RE .sp .ne 2 .mk .na \fB\fBENOLINK\fR\fR .ad .RS 11n .rt The \fIfildes\fR argument points to a remote machine and the link to that machine is no longer active. .RE .sp .LP The \fBfchmod()\fR function will fail if: .sp .ne 2 .mk .na \fB\fBEBADF\fR\fR .ad .RS 11n .rt The \fIfildes\fR argument is not an open file descriptor .RE .sp .ne 2 .mk .na \fB\fBENOLINK\fR\fR .ad .RS 11n .rt The \fIpath\fR argument points to a remote machine and the link to that machine is no longer active. .RE .sp .LP The \fBfchmodat()\fR function will fail if: .sp .ne 2 .mk .na \fB\fBEACCES\fR\fR .ad .RS 10n .rt \fIfd\fR was not opened with \fBO_SEARCH\fR and the permissions of the directory underlying \fIfd\fR do not permit directory searches. .RE .sp .ne 2 .mk .na \fB\fBEBADF\fR\fR .ad .RS 10n .rt The \fIpath\fR argument does not specify an absolute path and the \fIfd\fR argument is neither \fBAT_FDCWD\fR nor a valid file descriptor open for reading or searching. .RE .sp .LP The \fBchmod()\fR, \fBfchmod()\fR, and \fBfchmodat()\fR functions may fail if: .sp .ne 2 .mk .na \fB\fBEINTR\fR\fR .ad .RS 10n .rt A signal was caught during execution of the function. .RE .sp .ne 2 .mk .na \fB\fBEINVAL\fR\fR .ad .RS 10n .rt The value of the \fImode\fR argument is invalid. .RE .sp .LP The \fBchmod()\fR and \fBfchmodat()\fR functions may fail if: .sp .ne 2 .mk .na \fB\fBELOOP\fR\fR .ad .RS 16n .rt More than {\fBSYMLOOP_MAX\fR} symbolic links were encountered during the resolution of the \fIpath\fR argument. .RE .sp .ne 2 .mk .na \fB\fBENAMETOOLONG\fR\fR .ad .RS 16n .rt 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 .mk .na \fB\fBEINVAL\fR\fR .ad .RS 10n .rt The \fIfildes\fR argument refers to a pipe and the system disallows execution of this function on a pipe. .RE .sp .LP The \fBfchmodat()\fR function may fail if: .sp .ne 2 .mk .na \fB\fBEINVAL\fR\fR .ad .RS 14n .rt The value of the \fIflag\fR argument is invalid .RE .sp .ne 2 .mk .na \fB\fBENOTDIR\fR\fR .ad .RS 14n .rt The \fIpath\fR argument is not an absolute path and \fIfd\fR is neither \fBAT_FDCWD\fR nor a file descriptor associated with a directory .RE .sp .ne 2 .mk .na \fB\fBEOPNOTSUPP\fR\fR .ad .RS 14n .rt The \fBAT_SYMLINK_NOFOLLOW\fR bit is set in the \fIflag\fR argument, \fIpath\fR names a symbolic link, and the system does not support changing the mode of a symbolic link. .RE .SH EXAMPLES .LP \fBExample 1\fR Set 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 <sys/stat.h> const char *path; \&... chmod(path, S_IRUSR|S_IRGRP|S_IROTH); .fi .in -2 .sp .LP \fBExample 2\fR Set 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 <sys/stat.h> const char *path; \&... chmod(path, S_IRWXU); .fi .in -2 .sp .LP \fBExample 3\fR Set 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 <sys/stat.h> #define CHANGEFILE "/etc/myfile" \&... chmod(CHANGEFILE, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH); .fi .in -2 .sp .LP \fBExample 4\fR Set and Check 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 <sys/stat.h> int status; struct stat buffer; \&... chmod("/home/cnd/mod1", S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH); status = stat("/home/cnd/mod1", &buffer); if (status != 0) { perror("stat: /home/cnd/mod1"); } else if ((buffer.st_mode & S_IAMB) != (S_IRWXU|S_IRWXG|S_IROTH|S_IWOTH)) { /* Handle failure */ } .fi .in -2 .sp .SH USAGE .sp .LP If \fBchmod()\fR, \fBfchmod()\fR, or \fBfchmodat()\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 .sp .LP See \fBattributes\fR(7) for descriptions of the following attributes: .sp .TS tab( ) box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Committed _ MT-Level Async-Signal-Safe _ Standard See \fBstandards\fR(7). .TE .sp .SH SEE ALSO .sp .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(7), \fBprivileges\fR(7), \fBstandards\fR(7), \fBsysattr\fR(7) .SH HISTORY .sp .LP The \fBchmod()\fR and \fBfchmod()\fR functions have been included in all Sun and Oracle releases of Solaris. .sp .LP The \fBfchmodat()\fR function was added to Solaris in the Solaris 11.0 release.