date and time created 83/02/24 12:56:06 by mckusick

[unix-history] / usr / src / usr.bin / learn / learn / mysys.c

#ifndef lint
static char sccsid[] = "@(#)mysys.c     4.1     (Berkeley)      %G%";
#endif not lint

#include "stdio.h"
#include "signal.h"

#define EASY    1
#define MEDIUM  2
#define HARD    3

mysys(s)
char *s;
{
       /* like "system" but rips off "mv", etc.*/
       /* also tries to guess if can get away with exec cmd */
       /* instead of sh cmd */
       char p[300];
       char *np[40];
       register char *t;
       int nv, type, stat;

       type = EASY;    /* we hope */
       for (t = s; *t && type != HARD; t++) {
               switch (*t) {
               case '*': 
               case '[': 
               case '?': 
               case '>': 
               case '<': 
               case '$':
               case '\'':
               case '"':
                       type = MEDIUM;
                       break;
               case '|': 
               case ';': 
               case '&':
                       type = HARD;
                       break;
               }
       }
       switch (type) {
       case HARD:
               return(system(s));
       case MEDIUM:
               strcpy(p, "exec ");
               strcat(p, s);
               return(system(p));
       case EASY:
               strcpy(p,s);
               nv = getargs(p, np);
               t=np[0];
               if ((strcmp(t, "mv") == 0)||
                   (strcmp(t, "cp") == 0)||
                   (strcmp(t, "rm") == 0)||
                   (strcmp(t, "ls") == 0) ) {
                       if (fork() == 0) {
                               char b[100];
                               signal(SIGINT, SIG_DFL);
                               strcpy(b, "/bin/");
                               strcat(b, t);
                               np[nv] = 0;
                               execv(b, np);
                               fprintf(stderr, "Execv failed\n");
                               exit(1);
                       }
                       wait(&stat);
                       return(stat);
               }
               return(system(s));
       }
}

/*
* system():
*      same as library version, except that resets
*      default handling of signals in child, so that
*      user gets the behavior he expects.
*/

system(s)
char *s;
{
       int status, pid, w;
       register int (*istat)(), (*qstat)();

       istat = signal(SIGINT, SIG_IGN);
       qstat = signal(SIGQUIT, SIG_IGN);
       if ((pid = fork()) == 0) {
               signal(SIGINT, SIG_DFL);
               signal(SIGQUIT, SIG_DFL);
               execl("/bin/sh", "sh", "-c", s, 0);
               _exit(127);
       }
       while ((w = wait(&status)) != pid && w != -1)
               ;
       if (w == -1)
               status = -1;
       signal(SIGINT, istat);
       signal(SIGQUIT, qstat);
       return(status);
}

getargs(s, v)
char *s, **v;
{
       int i;

       i = 0;
       for (;;) {
               v[i++]=s;
               while (*s != 0 && *s!=' '&& *s != '\t')
                       s++;
               if (*s == 0)
                       break;
               *s++ =0;
               while (*s == ' ' || *s == '\t')
                       s++;
               if (*s == 0)
                       break;
       }
       return(i);
}