60 lines
1.4 KiB
C
Executable file
60 lines
1.4 KiB
C
Executable file
/*
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* (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
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* See the copyright notice in the ACK home directory, in the file "Copyright".
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*/
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/* $Header$ */
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#if defined(_POSIX_SOURCE)
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#include <sys/types.h>
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#endif
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#include <stdlib.h>
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#include <signal.h>
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extern pid_t _fork(void);
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extern pid_t _wait(int *);
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extern void _exit(int);
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extern void _execve(const char *path, const char ** argv, const char ** envp);
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extern int _close(int);
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#define FAIL 127
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extern const char ***_penviron;
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static const char *exec_tab[] = {
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"sh", /* argv[0] */
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"-c", /* argument to the shell */
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NULL, /* to be filled with user command */
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NULL /* terminating NULL */
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};
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int
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system(const char *str)
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{
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int pid, exitstatus, waitval;
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int i;
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if ((pid = _fork()) < 0) return str ? -1 : 0;
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if (pid == 0) {
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for (i = 3; i <= 20; i++)
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_close(i);
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if (!str) str = "cd ."; /* just testing for a shell */
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exec_tab[2] = str; /* fill in command */
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_execve("/bin/sh", exec_tab, *_penviron);
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/* get here if execve fails ... */
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_exit(FAIL); /* see manual page */
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}
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while ((waitval = _wait(&exitstatus)) != pid) {
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if (waitval == -1) break;
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}
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if (waitval == -1) {
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/* no child ??? or maybe interrupted ??? */
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exitstatus = -1;
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}
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if (!str) {
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if (exitstatus == FAIL << 8) /* execve() failed */
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exitstatus = 0;
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else exitstatus = 1; /* /bin/sh exists */
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}
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return exitstatus;
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}
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