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environ.c
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environ.c
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/*
* =====================================================================================
* Filename : environ.c
* Description : environment variable
* Version : 0.1
* Created : 03/29/14 14:40
* Author : Liu Xue Yang (LXY), liuxueyang457@163.com
* Motto : How about today?
* =====================================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main ( int argc, char *argv[] )
{
char *var, *value;
if ( 1 == argc || 3 < argc ) {
fprintf ( stderr, "usage: environ var [value]\n");
exit(1);
}
var = argv[1];
value = getenv(var);
if ( value ) {
printf ( "Variable %s has value %s\n", var, value);
}
else {
printf ( "Variable %s has no value\n", var);
}
if ( 3 == argc ) {
char *string;
value = argv[2];
string = malloc(strlen(var) + strlen(value) + 2);
if ( !string ) {
fprintf ( stderr, "out of memory\n");
exit(1);
}
strcpy(string, var);
strcat(string, "=");
strcat(string, value);
printf ( "Calling putenv with: %s\n", string);
if ( 0 != putenv(string) ) {
fprintf ( stderr, "putenv failed\n");
free(string);
exit(1);
}
value = getenv(var);
if ( value ) {
printf ( "New value of %s is %s\n", var, value);
}
else {
printf ( "New value of %s is null??\n", var);
}
}
return EXIT_SUCCESS;
} /* ---------- end of function main ---------- */