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string(3) Library Functions Manual string(3) NAME strcat, strcmp, strcpy, strdup - Perform operations on strings LIBRARY Standard C Library (libc.so, libc.a) SYNOPSIS #include <string.h> char *strcat( char *s1, const char *s2); int strcmp( const char *s1, const char *s2); char *strcpy( char *s1, const char *s2); char *strdup( const char *s1); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: strcat(), strcmp(), strcpy(): XPG4, XPG4-UNIX strdup(): XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS In strcat(), specifies the destination string for appending; in str- cmp(), specifies the first of two strings to compare; in strcpy(), specifies the destination string for the copying; and in strdup(), specifies the string to be duplicated. In strcat(), specifies the string to be appended to s1; in strcmp(), specifies the second of two strings to compare; and in strcpy(), specifies the source string for the copying. Note [Digital] If you pass a NULL pointer as one of the const char * or char * parameters of a string manipulation function, the function gen- erates a segmentation violation. To avoid the segmentation violation and cause the function to return zero, change the NULL pointer treat- ment for the process before issuing the call to the string manipulation function, as follows: Include the system header file sys/uswitch.h. Call the uswitch function, as described in the uswitch(2) reference page. The following program illustrates this procedure: #include <stdio.h> #include <sys/types.h> #include <sys/uswitch.h> main() { size_t retval; int uswitch_val; uswitch_val = uswitch(USC_GET,0); uswitch(USC_SET, uswitch_val | USW_NULLP); retval = strdup(NULL); DESCRIPTION The strcat() function appends a copy of the string pointed to by the s2 parameter (including the terminating null byte) to the end of the string pointed to by the s1 parameter. The initial byte of s2 over- writes the null byte at the end of the string pointed to by s1. When operating on overlapping strings, the behavior of this function is un- reliable. The strcmp() function compares the string pointed to by the s1 parame- ter to the string pointed to by the s2 parameter. The sign of a nonzero value returned by strcmp() is determined by the sign of the difference between the values of the first pair of bytes (both inter- preted as unsigned char) that differ in the two compared objects. The strcmp() function compares strings based on the machine collating order. It does not use the locale-dependent sorting order. Use the strcoll() or wcscoll() functions for locale-dependent sorting. The strcpy() function copies the string pointed to by the s2 parameter (including the terminating null byte) to the location pointed to by the s1 parameter. When operating on overlapping strings, the behavior of this function is unreliable. The strdup() function returns a pointer to a new string that is an ex- act duplicate of the string pointed to by the s1 parameter. The mal- loc() function is used to allocate space for the new string. RETURN VALUES On successful completion, the strcat(), strcpy(), and strdup() func- tions return a pointer to the resulting string. Otherwise, these func- tions return a null pointer. The strdup() function sets errno to indi- cate the error. On successful completion, the strcmp() function returns an integer whose value is greater than, equal to, or less than 0 (zero), according to whether the s1 string is greater than, equal to, or less than the s2 string. ERRORS If the strdup() function fails, errno may be set to the following value: Insufficient storage space is available. RELATED INFORMATION Functions: malloc(3), memccpy(3), setlocale(3), strchr(3), strcoll(3), strlen(3), strncasecmp(3), strncat(3), strncmp(3), strncpy(3), strp- brk(3), strspn(3), strtok(3), strstr(3), strxfrm(3), swab(3), uswitch(2), wcscat(3), wcscmp(3), wcscpy(3) Standards: standards(5) delim off string(3)