strcat, strcmp, strcpy, strdup - Perform operations on strings
Standard C Library (libc.so, libc.a)
const char *s2);
const char *s1,
const char *s2);
const char *s2);
const char *s1);
Interfaces documented on this reference page conform to industry standards as follows:
strcat(), strcmp(), strcpy(): XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
In strcat(), specifies the destination string for appending; in strcmp(), 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.
[Digital] If you pass a NULL pointer as one of the const char * or char * parameters of a string manipulation function, the function generates a segmentation violation. To avoid the segmentation violation and cause the function to return zero, change the NULL pointer treatment 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>
uswitch_val = uswitch(USC_GET,0);
uswitch(USC_SET, uswitch_val | USW_NULLP);
retval = strdup(NULL);
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 overwrites the null byte at the end of the string pointed to by s1. When operating on overlapping strings, the behavior of this function is unreliable.
The strcmp() function compares the string pointed to by the s1 parameter 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 interpreted 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 exact duplicate of the string pointed to by the s1 parameter. The malloc() function is used to allocate space for the new string.
On successful completion, the strcat(), strcpy(), and strdup() functions return a pointer to the resulting string. Otherwise, these functions return a null pointer. The strdup() function sets errno to indicate 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.
If the strdup() function fails, errno may be set to the following value: Insufficient storage space is available.
Functions: malloc(3), memccpy(3), setlocale(3), strchr(3), strcoll(3), strlen(3), strncasecmp(3), strncat(3), strncmp(3), strncpy(3), strpbrk(3), strspn(3), strtok(3), strstr(3), strxfrm(3), swab(3), uswitch(2), wcscat(3), wcscmp(3), wcscpy(3)
Standards: standards(5) delim off