dirname.1p (6352B)
- '\" et
- .TH DIRNAME "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH 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.
- .\"
- .SH NAME
- dirname
- \(em return the directory portion of a pathname
- .SH SYNOPSIS
- .LP
- .nf
- dirname \fIstring\fR
- .fi
- .SH DESCRIPTION
- The
- .IR string
- operand shall be treated as a pathname, as defined in the Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 3.271" ", " "Pathname".
- The string
- .IR string
- shall be converted to the name of the directory containing the
- filename corresponding to the last pathname component in
- .IR string ,
- performing actions equivalent to the following steps in order:
- .IP " 1." 4
- If
- .IR string
- is
- .BR // ,
- skip steps 2 to 5.
- .IP " 2." 4
- If
- .IR string
- consists entirely of
- <slash>
- characters,
- .IR string
- shall be set to a single
- <slash>
- character. In this case, skip steps 3 to 8.
- .IP " 3." 4
- If there are any trailing
- <slash>
- characters in
- .IR string ,
- they shall be removed.
- .IP " 4." 4
- If there are no
- <slash>
- characters remaining in
- .IR string ,
- .IR string
- shall be set to a single
- <period>
- character. In this case, skip steps 5 to 8.
- .IP " 5." 4
- If there are any trailing non-\c
- <slash>
- characters in
- .IR string ,
- they shall be removed.
- .IP " 6." 4
- If the remaining
- .IR string
- is
- .BR // ,
- it is implementation-defined whether steps 7 and 8 are skipped or
- processed.
- .IP " 7." 4
- If there are any trailing
- <slash>
- characters in
- .IR string ,
- they shall be removed.
- .IP " 8." 4
- If the remaining
- .IR string
- is empty,
- .IR string
- shall be set to a single
- <slash>
- character.
- .P
- The resulting string shall be written to standard output.
- .SH OPTIONS
- None.
- .SH OPERANDS
- The following operand shall be supported:
- .IP "\fIstring\fR" 10
- A string.
- .SH STDIN
- Not used.
- .SH "INPUT FILES"
- None.
- .SH "ENVIRONMENT VARIABLES"
- The following environment variables shall affect the execution of
- .IR dirname :
- .IP "\fILANG\fP" 10
- Provide a default value for the internationalization variables that are
- unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 8.2" ", " "Internationalization Variables"
- for the precedence of internationalization variables used to determine
- the values of locale categories.)
- .IP "\fILC_ALL\fP" 10
- If set to a non-empty string value, override the values of all the
- other internationalization variables.
- .IP "\fILC_CTYPE\fP" 10
- 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).
- .IP "\fILC_MESSAGES\fP" 10
- .br
- Determine the locale that should be used to affect the format and
- contents of diagnostic messages written to standard error.
- .IP "\fINLSPATH\fP" 10
- Determine the location of message catalogs for the processing of
- .IR LC_MESSAGES .
- .SH "ASYNCHRONOUS EVENTS"
- Default.
- .SH STDOUT
- The
- .IR dirname
- utility shall write a line to the standard output in the following
- format:
- .sp
- .RS 4
- .nf
- "%s\en", <\fIresulting string\fR>
- .fi
- .P
- .RE
- .SH STDERR
- The standard error shall be used only for diagnostic messages.
- .SH "OUTPUT FILES"
- None.
- .SH "EXTENDED DESCRIPTION"
- None.
- .SH "EXIT STATUS"
- The following exit values shall be returned:
- .IP "\00" 6
- Successful completion.
- .IP >0 6
- An error occurred.
- .SH "CONSEQUENCES OF ERRORS"
- Default.
- .LP
- .IR "The following sections are informative."
- .SH "APPLICATION USAGE"
- The definition of
- .IR pathname
- specifies implementation-defined behavior for pathnames starting with
- two
- <slash>
- characters. Therefore, applications shall not arbitrarily add
- <slash>
- characters to the beginning of a pathname unless they can ensure
- that there are more or less than two or are prepared to deal with the
- implementation-defined consequences.
- .SH EXAMPLES
- The EXAMPLES section of the
- \fIbasename\fR()
- function (see the System Interfaces volume of POSIX.1\(hy2017,
- .IR "\fIbasename\fR\^(\|)")
- includes a table showing examples of the results of processing several
- sample pathnames by the
- \fIbasename\fR()
- and
- \fIdirname\fR()
- functions and by the
- .IR basename
- and
- .IR dirname
- utilities.
- .P
- See also the examples for the
- .IR basename
- utility.
- .SH RATIONALE
- The behaviors of
- .IR basename
- and
- .IR dirname
- in this volume of POSIX.1\(hy2017 have been coordinated so that when
- .IR string
- is a valid pathname:
- .sp
- .RS 4
- .nf
- $(basename -- "\fIstring\fP")
- .fi
- .P
- .RE
- .P
- would be a valid filename for the file in the directory:
- .sp
- .RS 4
- .nf
- $(dirname -- "\fIstring\fP")
- .fi
- .P
- .RE
- .P
- This would not work for the versions of these utilities in early proposals
- due to the way processing of trailing
- <slash>
- characters was specified. Consideration was given to leaving processing
- unspecified if there were trailing
- <slash>
- characters, but this cannot be done; the Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 3.271" ", " "Pathname"
- allows trailing
- <slash>
- characters. The
- .IR basename
- and
- .IR dirname
- utilities have to specify consistent handling for all valid pathnames.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "Section 2.5" ", " "Parameters and Variables",
- .IR "\fIbasename\fR\^"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 3.271" ", " "Pathname",
- .IR "Chapter 8" ", " "Environment Variables"
- .P
- The System Interfaces volume of POSIX.1\(hy2017,
- .IR "\fIbasename\fR\^(\|)",
- .IR "\fIdirname\fR\^(\|)"
- .\"
- .SH 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 .
- .PP
- 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 .