Strcmp

In POSIX and in the programming language C, strcmp is a function in the C standard library (declared in string.h) that compares two C strings.

The prototype according ISO/IEC 9899:1999, 7.21.4.2 :int strcmp(const char *s1, const char *s2);

strcmp returns 0 when the strings are equal, a negative integer when s1 is less than s2, or a positive integer if s1 is greater than s2, according to the lexicographical order.

A variant of strcmp exists called strncmp that only compares the strings up to a certain point.

Example

#include
#include
#include

int main (int argc, char **argv){ int v;

if (argc < 3) { fprintf (stderr, "This program takes 2 arguments. "); return EXIT_FAILURE; }

v = strcmp (argv [1] , argv [2] );

if (v < 0) printf ("'%s' is less than '%s'. ", argv [1] , argv [2] ); else if (v = 0) printf ("'%s' equals '%s'. ", argv [1] , argv [2] ); else if (v > 0) printf ("'%s' is greater than '%s'. ", argv [1] , argv [2] );

return 0;}The above code is a working sample that prints whether the first argument is less than, equal to or greater than the second.

A possible implementation is (P.J. Plauger, The Standard C Library, 1992):int strcmp (const char * s1, const char * s2){

for(; *s1 = *s2; ++s1, ++s2) if(*s1 = 0) return 0; return *(unsigned char *)s1 < *(unsigned char *)s2 ? -1 : 1;}However, most real-world implementations will have various optimization tricks to reduce the execution time of the function.