mirror of https://github.com/mkerrisk/man-pages
68 lines
2.6 KiB
Groff
68 lines
2.6 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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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.\" manual page may be incorrect or out-of-date.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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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Interchanged 'needle' and 'haystack'; added history, aeb, 980113.
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.TH MEMMEM 3 1998-01-13 "GNU" "Linux Programmer's Manual"
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.SH NAME
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memmem \- locate a substring
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.SH SYNOPSIS
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.nf
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.B #define _GNU_SOURCE
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.B #include <string.h>
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.sp
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.BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
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.BI " const void *" needle ", size_t " needlelen );
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.fi
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.SH DESCRIPTION
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The
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.BR memmem ()
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function finds the start of the first occurrence
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of the substring \fIneedle\fP of length \fIneedlelen\fP in the memory
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area \fIhaystack\fP of length \fIhaystacklen\fP.
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.SH "RETURN VALUE"
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The
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.BR memmem ()
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function returns a pointer to the beginning of the
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substring, or NULL if the substring is not found.
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.SH "CONFORMING TO"
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This function is a GNU extension.
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.SH BUGS
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This function was broken in Linux libraries up to and including libc 5.0.9;
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there the \fIneedle\fP and \fIhaystack\fP arguments were interchanged,
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and a pointer to the end of the first occurrence of \fIneedle\fP
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was returned.
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Since libc 5.0.9 is still widely used, this is a
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dangerous function to use.
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.br
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Both old and new libc's have the bug that if \fIneedle\fP is empty
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\fIhaystack\-1\fP (instead of \fIhaystack\fP) is returned.
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And glibc 2.0 makes it worse, and returns a pointer to the
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last byte of \fIhaystack\fP.
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This is fixed in glibc 2.1.
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.SH "SEE ALSO"
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.BR strstr (3),
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.BR feature_test_macros (7)
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