.TH STRING 3 "19 January 1983" .SH NAME strcat, strncat, strcmp, strncmp, strcpy, strncpy, strlen, index, rindex \- string operations .SH SYNOPSIS .nf .B char *strcat(s1, s2) .B char *s1, *s2; .PP .B char *strncat(s1, s2, n) .B char *s1, *s2; .PP .B strcmp(s1, s2) .B char *s1, *s2; .PP .B strncmp(s1, s2, n) .B char *s1, *s2; .PP .B char *strcpy(s1, s2) .B char *s1, *s2; .PP .B char *strncpy(s1, s2, n) .B char *s1, *s2; .PP .B strlen(s) .B char *s; .PP .B char *index(s, c) .B char *s, c; .PP .B char *rindex(s, c) .B char *s, c; .fi .SH DESCRIPTION These functions operate on null-terminated strings. They do not check for overflow of any receiving string. .PP .I Strcat appends a copy of string .I s2 to the end of string .IR s1 . .I Strncat copies at most .I n characters. Both return a pointer to the null-terminated result. .PP .I Strcmp compares its arguments and returns an integer greater than, equal to, or less than 0, according as .I s1 is lexicographically greater than, equal to, or less than .IR s2 . .I Strncmp makes the same comparison but looks at at most .I n characters. .PP .I Strcpy copies string .I s2 to .I s1, stopping after the null character has been moved. .I Strncpy copies exactly .I n characters, truncating or null-padding .I s2; the target may not be null-terminated if the length of .I s2 is .I n or more. Both return .IR s1 . .PP .I Strlen returns the number of non-null characters in .IR s . .PP .I Index .RI ( rindex ) returns a pointer to the first (last) occurrence of character .I c in string .I s, or zero if .I c does not occur in the string. .SH BUGS .I Strcmp uses native character comparison, which is signed on the Sun Processor. .LP On PDP-11's and VAX'en, a source pointer of zero (0) can generally be used to indicate a null string. On the Sun processor (and on some other machines), a zero pointer is an error and results in an abort of the program. Programmers using NULL to represent an empty string should be aware of this portability issue.