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umask(1) General Commands Manual umask(1) NAME umask - Displays or sets the file mode creation mask SYNOPSIS umask [-S] ask] Note The C shell has a built-in version of the umask command. If you are using the C shell, and want to guarantee that you are using the command described here, you must specify the full path /usr/bin/umask. See the csh(1) reference page for a description of the built-in command. STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: umask: XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. OPTIONS Produce symbolic output. Output is produced in a format that is recognized on a subse- quent invocation of umask as a mask operand to restore the pre- vious file mode creation mask. If the -S option is not used, output is displayed as an octal integer, but is still usable as input on a subsequent invocation of the umask command. OPERANDS A string specifying the new file mode creation mask. This string may may be an octal value or a symbolic_mode value. For a symbolic_mode value, the new value of the file mode cre- ation mask is the logical complement of the file permission bits portion of the file mode specified by the symbolic_mode string. In a symbolic_mode value, the characters + and - are interpreted relative to the current file mode creation mask; + causes the bits for the indicated permissions to be cleared in the mask; - causes the bits for the indicated permissions to be set in the mask. The file mode creation mask is set to the resulting numeric value. In the obsolescent octal integer form of mode, the specified bits are set in the file mode creation mask. DESCRIPTION The umask command sets the file mode creation mask of the current shell execution environment to the value specified by the mask operand. This mask affects the initial value of the file permission bits of subsequently created files. If the mask operand is not specified, the umask command writes the value of the invoking process's file mode creation mask to standard output. If the -S option is specified, the output is in the following format: "u=%s,g=%s,o=%s\n", <owner permissions>, <group permissions>, <other permissions>" The three values are combinations of letters from the set {r, w, x}; the presence of a letter indicates that the corresponding bit is clear in the file mode creation mask. NOTES Any mask operand such as -r, -w, -x, or anything beginning with a hy- phen, must be preceded by -- to keep it from being interpreted as a op- tion. Since umask affects the current shell execution environment, it is provided as a shell regular built-in. In contrast to the negative permission logic provided by the file mode creation mask and the octal number form of the mask argument, the symbolic form of the mask operand specifies those permissions that are left alone. Although the refer- ences to octal modes are obsolescent in the ISO/IEC 9945-2:1993 stan- dard, they are maintained for portable applications until further no- tice. RESTRICTIONS If umask is called in a subshell or separate utility execution environ- ment, it does not affect the file mode creation mask of the caller's environment. A separate execution environment could be one of the fol- lowing: (umask 002) nohup umask ... find . -exec umask ... \; EXIT STATUS The following exit values are returned: The file mode creation mask was successfully changed, or no mask operand was supplied. An error oc- curred. EXAMPLES To set the file mode creation mask so that subsequently created files have their write by all others bit cleared, enter either of the follow- ing commands: umask a=rx,ug+w umask 002 If the file mode creation mask was set with either of the above commands, the umask command can be used to write out the current value of the mask. To write the value in octal format, enter: umask This provides the output: 0002 To write the value in symbolic format, enter: umask -S This provides the output: u=rwx,g=rwx,o=rx The following se- quence of commands is an example of how to save the current file mode creation mask and later restore the value using the umask command and octal integer formats. Examine the current value of the mask: umask The current mask is reported as: 022 Save the current value, and verify the saved value: SAVEMASK =`umask` echo $SAVEMASK The saved value is reported as: 022 Change the current mask: umask 444 Verify the change: umask The new mask is reported: 0444 Restore the previous mask: umask $SAVEMASK Verify the re- stored value: umask The value is now restored: 022 The following sequence of commands is an example of how to save the current file mode creation mask and later restore the value using the umask command and symbolic_mode formats. Examine the current value of the mask: umask -S The current mask is reported as: u=rwx,g=rx,o=rx Save the cur- rent value, and verify the saved value: SAVEMASK=`umask -S` echo $SAVEMASK The saved value is reported as: u=rwx,g=rx,o=rx Change the cur- rent mask: umask a= Verify the change: umask -S The new mask is reported: u=,g=,o= Restore the previous mask: umask $SAVEMASK Verify the restored value: umask -S The value is now restored: u=rwx,g=rx,o=rx To set the file mode creation mask so that subsequently created files have all their write bits cleared, enter: umask -- -w ENVIRONMENT VARIABLES The following environment variables affect the execution of umask: Pro- vides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization vari- ables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, over- rides the values of all the other internationalization variables. De- termines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi- byte characters in arguments). Determines the locale for the format and contents of diagnostic messages written to standard error. Deter- mines the location of message catalogues for the processing of LC_MES- SAGES. SEE ALSO Commands: chmod(1) Functions: chmod(2), umask(2) Standards: standards(5) umask(1)