150 lines
3.3 KiB
Groff
150 lines
3.3 KiB
Groff
.\" Copyright (c) 1980 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)string.3 6.1 (Berkeley) 5/15/85
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.\"
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.TH STRING 3 "May 15, 1985"
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.UC 4
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.SH NAME
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string, strcat, strncat, strcmp, strncmp, strcpy, strncpy, strlen, strchr, strrchr, strerror, memcmp, memcpy, memmove, memchr, memset, index, rindex \- string operations
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.SH SYNOPSIS
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.nf
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.ft B
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#include <string.h>
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char *strcat(char *\fIs1\fP, const char *\fIs2\fP)
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char *strncat(char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)
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int strcmp(const char *\fIs1\fP, const char *\fIs2\fP)
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int strncmp(const char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)
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char *strcpy(char *\fIs1\fP, const char *\fIs2\fP)
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char *strncpy(char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)
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size_t strlen(const char *\fIs\fP)
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char *strchr(const char *\fIs\fP, int \fIc\fP)
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char *strrchr(const char *\fIs\fP, int \fIc\fP)
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char *strerror(int \fIerrnum\fP)
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int memcmp(const void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)
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void *memcpy(void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)
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void *memmove(void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)
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void *memchr(const void *\fIs\fP, int \fIc\fP, size_t \fIn\fP)
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void *memset(void *\fIs\fP, int \fIc\fP, size_t \fIn\fP)
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char *index(const char *\fIs\fP, int \fIc\fP)
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char *rindex(const char *\fIs\fP, int \fIc\fP)
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.ft R
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.fi
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.SH DESCRIPTION
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These functions operate on null-terminated strings.
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They do not check for overflow of any receiving string.
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.PP
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.B Strcat
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appends a copy of string
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.I s2
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to the end of string
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.IR s1 .
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.B Strncat
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copies at most
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.I n
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characters. Both return a pointer to the null-terminated result.
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.PP
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.B Strcmp
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compares its arguments and returns an integer
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greater than, equal to, or less than 0, according as
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.I s1
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is lexicographically greater than, equal to, or less than
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.IR s2 .
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.B Strncmp
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makes the same comparison but looks at at most
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.I n
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characters.
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.PP
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.B Strcpy
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copies string
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.I s2
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to
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.IR s1 ,
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stopping after the null character has been moved.
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.B Strncpy
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copies exactly
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.I n
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characters, truncating or null-padding
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.I s2;
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the target may not be null-terminated if the length of
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.I s2
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is
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.I n
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or more. Both return
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.IR s1 .
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.PP
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.B Strlen
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returns the number of non-null characters in
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.IR s .
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.PP
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.B Strchr
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.RB ( strrchr )
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returns a pointer to the first (last) occurrence of character
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.I c
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in string
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.I s,
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or null if
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.I c
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does not occur in the string.
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.PP
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.B Strerror
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returns the error string for the system call error
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.IR errnum .
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See
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.BR intro (2).
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.PP
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.B Memcmp
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is like
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.B strcmp
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except that the strings are memory blocks of length
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.IR n .
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Null characters are treated as ordinary characters.
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.PP
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.B Memcpy
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copies
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.I n
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bytes from the location pointed to by
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.I s2
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to
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.IR s1 .
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.B Memmove
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is like memcpy, except that it can handle overlap between the two strings.
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Both functions return
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.IR s1 .
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.PP
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.B Memchr
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returns a pointer to the first occurrence of character
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.I c
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in string
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.I s,
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or null if
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.I c
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does not occur in the string.
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.PP
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.B Memset
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sets
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.I n
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bytes to
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.I c
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starting at location
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.IR s .
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It returns
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.IR s .
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.PP
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.B Index
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and
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.B rindex
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are obsolete versions of
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.B strchr
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and
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.BR strrchr .
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New code should avoid using them.
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.SH NOTES
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Characters are compared as
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.BR "unsigned char" ,
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whether
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.B char
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itself is signed or not.
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