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fea681da | 1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
2a8bb904 MK |
2 | .\" and Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
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6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
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15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
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23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
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26 | .\" |
27 | .\" Modified Mon Apr 12 12:49:57 1993, David Metcalfe | |
28 | .\" Modified Sat Jul 24 18:56:22 1993, Rik Faith (faith@cs.unc.edu) | |
29 | .\" Modified Wed Feb 20 21:09:36 2002, Ian Redfern (redferni@logica.com) | |
2a8bb904 | 30 | .\" 2008-07-09, mtk, add rawmemchr() |
fea681da | 31 | .\" |
9ba01802 | 32 | .TH MEMCHR 3 2019-03-06 "" "Linux Programmer's Manual" |
fea681da | 33 | .SH NAME |
2a8bb904 | 34 | memchr, memrchr, rawmemchr \- scan memory for a character |
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35 | .SH SYNOPSIS |
36 | .nf | |
37 | .B #include <string.h> | |
dbfe9c70 | 38 | .PP |
fea681da | 39 | .BI "void *memchr(const void *" s ", int " c ", size_t " n ); |
dbfe9c70 | 40 | .PP |
fea681da | 41 | .BI "void *memrchr(const void *" s ", int " c ", size_t " n ); |
dbfe9c70 | 42 | .PP |
2a8bb904 | 43 | .BI "void *rawmemchr(const void *" s ", int " c ); |
fea681da | 44 | .fi |
68e4db0a | 45 | .PP |
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46 | .in -4n |
47 | Feature Test Macro Requirements for glibc (see | |
48 | .BR feature_test_macros (7)): | |
49 | .in | |
68e4db0a | 50 | .PP |
13a7959b | 51 | .BR memrchr (), |
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52 | .BR rawmemchr (): |
53 | _GNU_SOURCE | |
fea681da | 54 | .SH DESCRIPTION |
c13182ef | 55 | The |
63aa9df0 | 56 | .BR memchr () |
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57 | function scans the initial |
58 | .I n | |
59 | bytes of the memory | |
60 | area pointed to by | |
61 | .I s | |
62 | for the first instance of | |
63 | .IR c . | |
64 | Both | |
65 | .I c | |
66 | and the bytes of the memory area pointed to by | |
67 | .I s | |
68 | are interpreted as | |
69 | .IR "unsigned char" . | |
fea681da | 70 | .PP |
c13182ef | 71 | The |
63aa9df0 | 72 | .BR memrchr () |
c13182ef | 73 | function is like the |
63aa9df0 | 74 | .BR memchr () |
fea681da | 75 | function, |
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76 | except that it searches backward from the end of the |
77 | .I n | |
78 | bytes pointed to by | |
79 | .I s | |
80 | instead of forward from the beginning. | |
847e0d88 | 81 | .PP |
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82 | The |
83 | .BR rawmemchr () | |
84 | function is similar to | |
85 | .BR memchr (): | |
86 | it assumes (i.e., the programmer knows for certain) | |
9640b1b3 | 87 | that an instance of |
2a8bb904 | 88 | .I c |
9640b1b3 | 89 | lies somewhere in the memory area starting at the location pointed to by |
2a8bb904 | 90 | .IR s , |
9640b1b3 | 91 | and so performs an optimized search for |
e346bc5a | 92 | .IR c |
a0d6d887 | 93 | (i.e., no use of a count argument to limit the range of the search). |
9640b1b3 | 94 | If an instance of |
2a8bb904 | 95 | .I c |
9640b1b3 | 96 | is not found, the results are unpredictable. |
88d95555 | 97 | The following call is a fast means of locating a string's |
2a8bb904 | 98 | terminating null byte: |
e646a1ba | 99 | .PP |
2a8bb904 | 100 | .in +4n |
e646a1ba | 101 | .EX |
d1a71985 | 102 | char *p = rawmemchr(s,\ \(aq\e0\(aq); |
b8302363 | 103 | .EE |
2a8bb904 | 104 | .in |
47297adb | 105 | .SH RETURN VALUE |
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106 | The |
107 | .BR memchr () | |
108 | and | |
109 | .BR memrchr () | |
110 | functions return a pointer | |
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111 | to the matching byte or NULL if the character does not occur in |
112 | the given memory area. | |
847e0d88 | 113 | .PP |
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114 | The |
115 | .BR rawmemchr () | |
116 | function returns a pointer to the matching byte, if one is found. | |
117 | If no matching byte is found, the result is unspecified. | |
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118 | .SH VERSIONS |
119 | .BR rawmemchr () | |
120 | first appeared in glibc in version 2.1. | |
847e0d88 | 121 | .PP |
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122 | .BR memrchr () |
123 | first appeared in glibc in version 2.2. | |
daecb330 | 124 | .SH ATTRIBUTES |
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125 | For an explanation of the terms used in this section, see |
126 | .BR attributes (7). | |
127 | .TS | |
128 | allbox; | |
129 | lbw32 lb lb | |
130 | l l l. | |
131 | Interface Attribute Value | |
132 | T{ | |
daecb330 PH |
133 | .BR memchr (), |
134 | .BR memrchr (), | |
daecb330 | 135 | .BR rawmemchr () |
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136 | T} Thread safety MT-Safe |
137 | .TE | |
47297adb | 138 | .SH CONFORMING TO |
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139 | .BR memchr (): |
140 | POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD. | |
847e0d88 | 141 | .PP |
c13182ef | 142 | The |
63aa9df0 | 143 | .BR memrchr () |
fea681da | 144 | function is a GNU extension, available since glibc 2.1.91. |
847e0d88 | 145 | .PP |
2a8bb904 | 146 | The |
c7cb2bdb | 147 | .BR rawmemchr () |
2a8bb904 | 148 | function is a GNU extension, available since glibc 2.1. |
47297adb | 149 | .SH SEE ALSO |
879091c9 | 150 | .BR bstring (3), |
52aa4b97 | 151 | .BR ffs (3), |
fea681da | 152 | .BR index (3), |
3924b70d | 153 | .BR memmem (3), |
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154 | .BR rindex (3), |
155 | .BR strchr (3), | |
156 | .BR strpbrk (3), | |
157 | .BR strrchr (3), | |
158 | .BR strsep (3), | |
159 | .BR strspn (3), | |
160 | .BR strstr (3), | |
161 | .BR wmemchr (3) |