util-linux-ng-2.17.2/lib/setproctitle.c

/* proctitle code - we know this to work only on linux... */

/*
**  SETPROCTITLE -- set process title for ps (from sendmail)
**
**      Parameters:
**              fmt -- a printf style format string.
**
**      Returns:
**              none.
**
**      Side Effects:
**              Clobbers argv of our main procedure so ps(1) will
**              display the title.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include "setproctitle.h"

#ifndef SPT_BUFSIZE
#define SPT_BUFSIZE     2048
#endif

extern char** environ;

static char** argv0;
static int argv_lth;

void
initproctitle (int argc, char **argv) {
	int i;
	char **envp = environ;

	/*
	 * Move the environment so we can reuse the memory.
	 * (Code borrowed from sendmail.)
	 * WARNING: ugly assumptions on memory layout here;
	 *          if this ever causes problems, #undef DO_PS_FIDDLING
	 */
	for (i = 0; envp[i] != NULL; i++)
		continue;
	environ = (char **) malloc(sizeof(char *) * (i + 1));
	if (environ == NULL)
		return;
	for (i = 0; envp[i] != NULL; i++)
		if ((environ[i] = strdup(envp[i])) == NULL)
			return;
	environ[i] = NULL;

	argv0 = argv;
	if (i > 0)
		argv_lth = envp[i-1] + strlen(envp[i-1]) - argv0[0];
	else
		argv_lth = argv0[argc-1] + strlen(argv0[argc-1]) - argv0[0];
}	

#if 0
/* Nice code, but many places do not know about vsnprintf ... */
void
setproctitle (const char *fmt,...) {
	int        i;
	char       buf[SPT_BUFSIZE];
	va_list    ap;

	if (!argv0)
		return;

	va_start(ap, fmt);
	(void) vsnprintf(buf, SPT_BUFSIZE, fmt, ap);
	va_end(ap);

	i = strlen (buf);
	if (i > argv_lth - 2) {
		i = argv_lth - 2;
		buf[i] = '\0';
	}
	memset(argv0[0], '\0', argv_lth);       /* clear the memory area */
	(void) strcpy (argv0[0], buf);

	argv0[1] = NULL;
}
#else
void
setproctitle (const char *prog, const char *txt) {
        int        i;
        char       buf[SPT_BUFSIZE];

        if (!argv0)
                return;

	if (strlen(prog) + strlen(txt) + 5 > SPT_BUFSIZE)
		return;

        (void) sprintf(buf, "%s -- %s", prog, txt);

        i = strlen (buf);
        if (i > argv_lth - 2) {
                i = argv_lth - 2;
                buf[i] = '\0';
        }
	memset(argv0[0], '\0', argv_lth);       /* clear the memory area */
        (void) strcpy (argv0[0], buf);

        argv0[1] = NULL;
}
#endif