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- #include <stdlib.h>
- #include <stdio.h>
- #include <sys/types.h>
- #include <unistd.h>
- #include <sys/wait.h>
- #define MAXFORKS 20
- #define NSYSFILE 3
- #define tst(a,b) (*mode == 'r'? (b) : (a))
- #define RDR 0
- #define WTR 1
- struct a_fork {
- short done;
- short fd;
- int pid;
- int status;
- };
- static struct a_fork the_fork[MAXFORKS];
- FILE *
- popen(char *cmd, char *mode)
- {
- int p[2];
- int myside, hisside, pid;
- int i, ind;
- for (ind = 0; ind < MAXFORKS; ind++)
- if (the_fork[ind].pid == 0)
- break;
- if (ind == MAXFORKS)
- return NULL;
- if(pipe(p) < 0)
- return NULL;
- myside = tst(p[WTR], p[RDR]);
- hisside = tst(p[RDR], p[WTR]);
- switch (pid = fork()) {
- case -1:
- return NULL;
- case 0:
- /* myside and hisside reverse roles in child */
- close(myside);
- dup2(hisside, tst(0, 1));
- for (i=NSYSFILE; i<FOPEN_MAX; i++)
- close(i);
- execl("/bin/ape/sh", "sh", "-c", cmd, 0);
- _exit(1);
- default:
- the_fork[ind].pid = pid;
- the_fork[ind].fd = myside;
- the_fork[ind].done = 0;
- close(hisside);
- return(fdopen(myside, mode));
- }
- }
- int
- pclose(FILE *ptr)
- {
- int f, r, ind;
- int status;
- f = fileno(ptr);
- fclose(ptr);
- for (ind = 0; ind < MAXFORKS; ind++)
- if (the_fork[ind].fd == f && the_fork[ind].pid != 0)
- break;
- if (ind == MAXFORKS)
- return 0;
- if (!the_fork[ind].done) {
- do {
- r = wait(&status);
- for (f = 0; f < MAXFORKS; f++)
- if (the_fork[f].pid == r) {
- the_fork[f].done = 1;
- the_fork[f].status = status;
- break;
- }
- } while(r != the_fork[ind].pid && r != -1);
- the_fork[ind].status = r == -1 ? -1 : status;
- }
- the_fork[ind].pid = 0;
- return (the_fork[ind].status);
- }
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