time-to-botec

README.md (6432B)

---

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 # umask
 
 > Get/set the process mask.
 
 <section class="intro">
 
 A **mask** is a set of bits, each of which restricts how its corresponding permission is set for newly created files. On POSIX platforms, each file has a set of attributes that control who can read, write, or execute that file. Upon creating a file, file permissions must be set to an initial setting. The process mask restricts those permission settings.
 
 If the mask contains a bit set to `1`, the corresponding initial file permission is disabled. If the mask contains a bit set to `0`, the corresponding permission is left to be determined by the requesting process and the system. The process mask is thus a filter that **removes** permissions as a file is created; i.e., each bit set to a `1` removes its corresponding permission.
 
 In octal representation, a mask is a four digit number comprised as follows (using `0077` as an example):
 
 -   `0`: special permissions (setuid, setgid, sticky bit)
 -   `0`: (u)ser/owner permissions
 -   `7`: (g)roup permissions
 -   `7`: (o)thers/non-group permissions
 
 Octal codes correspond to the following permissions:
 
 -   `0`: read, write, execute
 -   `1`: read, write
 -   `2`: read, execute
 -   `3`: read
 -   `4`: write, execute
 -   `5`: write
 -   `6`: execute
 -   `7`: no permissions
 
 If provided fewer than four digits, the mask is left-padded with zeros. Note, however, that **only** the last three digits (i.e., the file permissions digits) of the mask are actually used when the mask is applied (i.e., `mask & 0777`).
 
 Permissions can be represented using the following symbolic form:
 
 ```text
 u=rwx,g=rwx,o=rwx
 ```
 
 where
 
 -   **u**: user permissions
 -   **g**: group permissions
 -   **o**: other/non-group permissions
 -   **r**: read
 -   **w**: write
 -   **x**: execute
 
 When setting permissions using symbolic notation, one may use a _mask expression_ of the form:
 
 ```text
 [<classes>]<operator><symbols>
 ```
 
 where `<classes>` may be a combination of
 
 -   **u**: user
 -   **g**: group
 -   **o**: other/non-group
 -   **a**: all
 
 `<symbols>` may be a combination of
 
 -   **r**: read
 -   **w**: write
 -   **x**: execute
 -   **X**: special execute
 -   **s**: setuid/gid on execution
 -   **t**: sticky
 
 and `<operator>` may be one of
 
 -   **+**: enable
 -   **-**: disable
 -   **=**: enable specified and disable unspecified permissions
 
 For example,
 
 -   `u-w`: disable user write permissions
 -   `u+w`: enable user write permissions
 -   `u=w`: enable user write permissions and disable user read and execute
 
 To specify multiple changes, one can specify a comma-separated list of mask expressions. For example,
 
 ```text
 u+rwx,g-x,o=r
 ```
 
 would enable user read, write, and execute permissions, disable group execute permissions, enable other read permissions, and disable other write and execute permissions.
 
 The `a` class indicates "all", which is the same as specifying `ugo`. This is the default class if a class is omitted when specifying permissions. For example, `+x` is equivalent to `a+x` which is equivalent to `ugo+x` which is equivalent to `u+x,g+x,o+x` and enables execution for all classes.
 
 </section>
 
 <!-- /.intro -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var umask = require( '@stdlib/process/umask' );
 ```
 
 #### umask( \[mask,] \[options] )
 
 Returns the process mask.
 
 ```javascript
 var mask = umask();
 // returns <number>
 ```
 
 To set the process mask, provide a `mask` argument. When provided a `mask`, the function returns the previous mask value.
 
 ```javascript
 var mask = umask();
 // returns <number>
 
 var prev = umask( 0 );
 // returns <number>
 
 var bool = ( prev === mask );
 // returns true
 ```
 
 The `mask` argument may be either an integer value or a `string` representing the mask using symbolic notation.
 
 ```javascript
 var mask = umask( 'u=rwx,g=rw,o=rw' );
 ```
 
 The function accepts the following `options`:
 
 -   **symbolic**: `boolean` indicating whether to return the mask in symbolic notation. Default: `false`.
 
 To return the process mask in symbolic notation, set the `symbolic` option to `true`.
 
 ```javascript
 var opts = {
     'symbolic': true
 };
 
 // Get the mask:
 var mask = umask( opts );
 // e.g., returns 'u=rwx,g=rw,o=rw'
 
 // Set the mask:
 mask = umask( 0, opts );
 // e.g., returns 'u=rwx,g=rw,o=rw'
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <section class="notes">
 
 ## Notes
 
 -   To set the process mask using an octal `string` (e.g., `0777`), use `parseInt` to convert the `string` to an integer value.
 
     ```javascript
     umask( parseInt( '0777', 8 ) );
     ```
 
 -   See [umask(2)][umask].
 
 </section>
 
 <!-- /.notes -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var lpad = require( '@stdlib/string/left-pad' );
 var umask = require( '@stdlib/process/umask' );
 
 var mask;
 var opts;
 
 // Print the process mask as an integer:
 mask = umask();
 console.log( mask.toString() );
 
 // Print the process mask as an octal string:
 console.log( lpad( mask.toString(), 4, '0' ) );
 
 // Print the process mask using symbolic notation:
 opts = {
     'symbolic': true
 };
 console.log( umask( opts ) );
 ```
 
 </section>
 
 <!-- /.examples -->
 
 * * *
 
 <section class="cli">
 
 ## CLI
 
 <section class="usage">
 
 ### Usage
 
 ```text
 Usage: umask [options]
 
 Options:
 
   -h,    --help                Print this message.
   -V,    --version             Print the package version.
   -p,    --print               Print the mask command.
   -S,    --symbolic            Print the mask using symbolic notation.
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <section class="examples">
 
 ### Examples
 
 ```bash
 $ umask
 ```
 
 To print the mask in command format, set the `-p` flag.
 
 ```bash
 $ umask -p
 ```
 
 </section>
 
 <!-- /.examples -->
 
 </section>
 
 <!-- /.cli -->
 
 <section class="links">
 
 [umask]: http://man7.org/linux/man-pages/man2/umask.2.html
 
 </section>
 
 <!-- /.links -->