putenv.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 73 行

/* putenv.c - (un) set an envariable */

#include "../h/mh.h"
#include <stdio.h>


extern  char **environ;

static nvmatch();

int     putenv (name, value)
register char  *name,
               *value;
{
    register int    i;
    register char **ep,
                  **nep,
                   *cp;

    if ((cp = malloc ((unsigned) (strlen (name) + strlen (value) + 2)))
	    == NULL)
	return 1;
    (void) sprintf (cp, "%s=%s", name, value);

    for (ep = environ, i = 0; *ep; ep++, i++)
	if (nvmatch (name, *ep)) {
	    *ep = cp;
	    return 0;
	}

    if ((nep = (char **) malloc ((unsigned) ((i + 2) * sizeof *nep))) == NULL)
	return 1;
    for (ep = environ, i = 0; *ep; nep[i++] = *ep++)
	continue;
    nep[i++] = cp;
    nep[i] = NULL;
    environ = nep;
    return 0;
}


int	unputenv (name)
char   *name;
{
    char  **ep,
          **nep;

    for (ep = environ; *ep; ep++)
	if (nvmatch (name, *ep))
	    break;
    if (*ep == NULL)
	return 1;

    for (nep = ep + 1; *nep; nep++)
	continue;
    *ep = *--nep;
    *nep = NULL;
    return 0;
}

/*  */

static nvmatch (s1, s2)
register char  *s1,
               *s2;
{
    while (*s1 == *s2++)
	if (*s1++ == '=')
	    return 1;

    return (*s1 == '\0' && *--s2 == '=');
}