MKFIFO(1P)

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME
mkfifo — make FIFO special files

SYNOPSIS

mkfifo [-m mode] file...

DESCRIPTION
The mkfifo utility shall create the FIFO special files specified by the operands, in the order specified.

For each file operand, the mkfifo utility shall perform actions equivalent to the mkfifo() function defined in the System Interfaces volume of POSIX.1-2017, called with the following arguments:

1.  The file operand is used as the path argument.

2.  The value of the bitwise-inclusive OR of S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH is used as the mode argument. (If the -m option is specified, the value of the mkfifo() mode argument is unspecified, but the FIFO shall at no time have permissions less restrictive than the -m mode option-argument.)

OPTIONS
The mkfifo utility shall conform to the Base Definitions volume of POSIX.1-2017, Section 12.2, Utility Syntax Guidelines.

The following option shall be supported:

-m mode
    Set the file permission bits of the newly-created FIFO to the specified mode value. The mode option-argument shall be the same as the mode operand defined for the chmod utility. In the symbolic_mode strings, the op characters '+' and '-' shall be interpreted relative to an assumed initial mode of a= rw.

OPERANDS
The following operand shall be supported:

file
    A pathname of the FIFO special file to be created.

STDIN
Not used.

INPUT FILES
None.

ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of mkfifo:

LANG
    Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1-2017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)

LC_ALL
    If set to a non-empty string value, override the values of all the other internationalization variables.

LC_CTYPE
    Determine 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).

LC_MESSAGES
    Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.

NLSPATH
    Determine the location of message catalogs for the processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS
Default.

STDOUT
Not used.

STDERR
The standard error shall be used only for diagnostic messages.

OUTPUT FILES
None.

EXTENDED DESCRIPTION
None.

EXIT STATUS
The following exit values shall be returned:

0   All the specified FIFO special files were created successfully.

>0  An error occurred.

CONSEQUENCES OF ERRORS
Default.

The following sections are informative.

APPLICATION USAGE
None.

EXAMPLES
None.

RATIONALE
This utility was added to permit shell applications to create FIFO special files.

The -m option was added to control the file mode, for consistency with the similar functionality provided by the mkdir utility.

Early proposals included a -p option similar to the mkdir -p option that created intermediate directories leading up to the FIFO specified by the final component. This was removed because it is not commonly needed and is not common practice with similar utilities.

The functionality of mkfifo is described substantially through a reference to the mkfifo() function in the System Interfaces volume of POSIX.1-2017. For example, by default, the mode of the FIFO file is affected by the file mode creation mask in accordance with the specified behavior of the mkfifo() function. In this way, there is less duplication of effort required for describing details of the file creation.

FUTURE DIRECTIONS
None.

SEE ALSO
chmod, umask

The Base Definitions volume of POSIX.1-2017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines

The System Interfaces volume of POSIX.1-2017, mkfifo()

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version 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 .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .