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 IEEE Std 1003.1-2001, called with the following
The file operand is used as the path
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 -mmode
The mkfifo utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
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
The following environment variables shall affect the execution of mkfifo:
Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
If set to a non-empty string value, override the values of
all the other internationalization variables.
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).
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the
processing of LC_MESSAGES.
This utility was added to permit shell applications to create FIFO special
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
IEEE Std 1003.1-2001. 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.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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