mirror of https://github.com/mkerrisk/man-pages
175 lines
4.4 KiB
Groff
175 lines
4.4 KiB
Groff
.\" Copyright (c) 2000 by Michael Kerrisk (mtk.manpages@gmail.com)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" License.
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.\" Created, 14 Dec 2000 by Michael Kerrisk
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.\"
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.TH BASENAME 3 2000-12-14 "GNU" "Linux Programmer's Manual"
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.SH NAME
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basename, dirname \- parse pathname components
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.SH SYNOPSIS
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.nf
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.B #include <libgen.h>
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.sp
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.BI "char *dirname(char *" path );
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.BI "char *basename(char *" path );
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.fi
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.SH DESCRIPTION
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Warning: there are two different functions
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.BR basename ()
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- see below.
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.LP
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The functions
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.BR dirname ()
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and
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.BR basename ()
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break a null-terminated pathname string into directory
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and filename components.
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In the usual case,
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.BR dirname ()
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returns the string up to, but not including, the final \(aq/\(aq, and
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.BR basename ()
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returns the component following the final \(aq/\(aq.
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Trailing \(aq/\(aq characters are not counted as part of the pathname.
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.PP
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If
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.I path
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does not contain a slash,
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.BR dirname ()
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returns the string "." while
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.BR basename ()
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returns a copy of
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.IR path .
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If
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.I path
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is the string "/", then both
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.BR dirname ()
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and
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.BR basename ()
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return the string "/".
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If
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.I path
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is a NULL pointer or points to an empty string, then both
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.BR dirname ()
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and
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.BR basename ()
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return the string ".".
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.PP
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Concatenating the string returned by
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.BR dirname (),
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a "/", and the string returned by
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.BR basename ()
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yields a complete pathname.
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.PP
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Both
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.BR dirname ()
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and
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.BR basename ()
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may modify the contents of
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.IR path ,
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so it may be desirable to pass a copy when calling one of
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these functions.
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.PP
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These functions may return pointers to statically allocated memory
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which may be overwritten by subsequent calls.
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Alternatively, they may return a pointer to some part of
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.IR path ,
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so that the string referred to by
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.I path
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should not be modified or freed until the pointer returned by
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the function is no longer required.
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.PP
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The following list of examples (taken from SUSv2)
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shows the strings returned by
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.BR dirname ()
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and
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.BR basename ()
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for different paths:
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.sp
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.nf
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.B "path dirname basename"
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"/usr/lib" "/usr" "lib"
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"/usr/" "/" "usr"
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"usr" "." "usr"
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"/" "/" "/"
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"." "." "."
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".." "." ".."
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.fi
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.SH "RETURN VALUE"
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Both
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.BR dirname ()
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and
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.BR basename ()
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return pointers to null-terminated strings.
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.SH "CONFORMING TO"
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POSIX.1-2001
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.SH NOTES
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There are two different versions of
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.BR basename ()
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- the POSIX version described above, and the GNU version, which one gets
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after
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.br
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.nf
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.B " #define _GNU_SOURCE"
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.br
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.B " #include <string.h>"
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.fi
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The GNU version never modifies its argument, and returns the
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empty string when
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.I path
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has a trailing slash, and in particular also when it is "/".
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There is no GNU version of
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.BR dirname ().
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.LP
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With glibc, one gets the POSIX version of
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.BR basename ()
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when
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.I <libgen.h>
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is included, and the GNU version otherwise.
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.SH BUGS
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In the glibc implementation of the POSIX versions of these functions
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they modify their argument, and segfault when called with a static string
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like "/usr/".
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Before glibc 2.2.1, the glibc version of
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.BR dirname ()
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did not correctly handle pathnames with trailing \(aq/\(aq characters,
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and generated a segfault if given a NULL argument.
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.SH EXAMPLE
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.in +4n
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.nf
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char *dirc, *basec, *bname, *dname;
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char *path = "/etc/passwd";
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dirc = strdup(path);
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basec = strdup(path);
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dname = dirname(dirc);
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bname = basename(basec);
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printf("dirname=%s, basename=%s\\n", dname, bname);
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.fi
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.in
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.SH "SEE ALSO"
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.BR basename (1),
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.BR dirname (1),
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.BR feature_test_macros (7)
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