ref: 2b1454e81c8ee4572408096f4593678d184da130
dir: /sys/man/2/strcat/
.TH STRCAT 2 .SH NAME strcat, strncat, strcmp, strncmp, cistrcmp, cistrncmp, strcpy, strncpy, strecpy, strlen, strchr, strrchr, strpbrk, strspn, strcspn, strtok, strdup, strstr, cistrstr \- string operations .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .ta \w'\fLchar* \fP'u .B char* strcat(char *s1, char *s2) .PP .B char* strncat(char *s1, char *s2, long n) .PP .B int strcmp(char *s1, char *s2) .PP .B int strncmp(char *s1, char *s2, long n) .PP .B int cistrcmp(char *s1, char *s2) .PP .B int cistrncmp(char *s1, char *s2, long n) .PP .B char* strcpy(char *s1, char *s2) .PP .B char* strecpy(char *s1, char *es1, char *s2) .PP .B char* strncpy(char *s1, char *s2, long n) .PP .B long strlen(char *s) .PP .B char* strchr(char *s, int c) .PP .B char* strrchr(char *s, int c) .PP .B char* strpbrk(char *s1, char *s2) .PP .B long strspn(char *s1, char *s2) .PP .B long strcspn(char *s1, char *s2) .PP .B char* strtok(char *s1, char *s2) .PP .B char* strdup(char *s) .PP .B char* strstr(char *s1, char *s2) .PP .B char* cistrstr(char *s1, char *s2) .SH DESCRIPTION The arguments .I s1, s2 and .I s point to null-terminated strings. The functions .IR strcat , .IR strncat , .IR strcpy , .IR strecpy , and .I strncpy all alter .IR s1 . .I Strcat and .I strcpy do not check for overflow of the array pointed to by .IR s1 . .PP .I Strcat appends a copy of string .I s2 to the end of string .IR s1 . .I Strncat appends at most .I n bytes. Each returns a pointer to the null-terminated result. .PP .I Strcmp compares its arguments and returns an integer less than, equal to, or greater than 0, according as .I s1 is lexicographically less than, equal to, or greater than .IR s2 . .I Strncmp makes the same comparison but examines at most .I n bytes. .I Cistrcmp and .I cistrncmp ignore ASCII case distinctions when comparing strings. The comparisons are made with unsigned bytes. .PP .I Strcpy copies string .I s2 to .IR s1 , stopping after the null byte has been copied. .I Strncpy copies exactly .I n bytes, truncating .I s2 or adding null bytes to .I s1 if necessary. The result will not be null-terminated if the length of .I s2 is .I n or more. Each function returns .IR s1 . .PP .I Strecpy copies bytes until a null byte has been copied, but writes no bytes beyond .IR es1 . If any bytes are copied, .I s1 is terminated by a null byte, and a pointer to that byte is returned. Otherwise, the original .I s1 is returned. .PP .I Strlen returns the number of bytes in .IR s , not including the terminating null byte. .PP .I Strchr .RI ( strrchr ) returns a pointer to the first (last) occurrence of byte .I c in string .IR s , or .L 0 if .I c does not occur in the string. The null byte terminating a string is considered to be part of the string. .PP .I Strpbrk returns a pointer to the first occurrence in string .I s1 of any byte from string .IR s2 , .L 0 if no byte from .I s2 exists in .IR s1 . .PP .I Strspn .RI ( strcspn ) returns the length of the initial segment of string .I s1 which consists entirely of bytes from (not from) string .IR s2 . .PP .I Strtok considers the string .I s1 to consist of a sequence of zero or more text tokens separated by spans of one or more bytes from the separator string .IR s2 . The first call, with pointer .I s1 specified, returns a pointer to the first byte of the first token, and will have written a null byte into .I s1 immediately following the returned token. The function keeps track of its position in the string between separate calls; subsequent calls, signified by .I s1 being .LR 0 , will work through the string .I s1 immediately following that token. The separator string .I s2 may be different from call to call. When no token remains in .IR s1 , .L 0 is returned. .PP .I Strdup returns a pointer to a distinct copy of the null-terminated string .I s in space obtained from .IR malloc (2) or .L 0 if no space can be obtained. .PP .I Strstr returns a pointer to the first occurrence of .I s2 as a substring of .IR s1 , or 0 if there is none. If .I s2 is the null string, .I strstr returns .IR s1 . .I Cistrstr operates analogously, but ignores ASCII case differences when comparing strings. .SH SOURCE All these routines have portable C implementations in .BR /sys/src/libc/port . Many also have machine-dependent assembly language implementations in .BR /sys/src/libc/$objtype . .SH SEE ALSO .IR memory (2), .IR rune (2), .IR runestrcat (2), .IR string (2) .SH BUGS These routines know nothing about .SM UTF. Use the routines in .IR rune (2) as appropriate. Note, however, that the definition of .SM UTF guarantees that .I strcmp compares .SM UTF strings correctly. .PP The outcome of overlapping moves varies among implementations.