73 lines
1.3 KiB
C
73 lines
1.3 KiB
C
/*
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* This code is identical to running
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* cat $1 | sort | uniq
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* in bash
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*/
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#include <stdio.h>
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#include <unistd.h>
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void run_cat(char* filename, int pfd[2]) {
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dup2(pfd[1], STDOUT_FILENO);
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close(pfd[0]);
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close(pfd[1]);
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char cmd[] = "/usr/bin/cat";
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char *args[] = {"cat", filename, NULL};
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execve(cmd, args, NULL);
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}
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void run_sort(int pfd1[2], int pfd2[2]) {
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dup2(pfd1[0], STDIN_FILENO);
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dup2(pfd2[1], STDOUT_FILENO);
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close(pfd1[0]);
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close(pfd1[1]);
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close(pfd2[0]);
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close(pfd2[1]);
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char cmd[] = "/usr/bin/sort";
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char *args[] = {"sort", NULL};
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execve(cmd, args, NULL);
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}
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void run_uniq(int pfd[2]) {
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dup2(pfd[0], STDIN_FILENO);
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close(pfd[0]);
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close(pfd[1]);
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char cmd[] = "/usr/bin/uniq";
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char *args[] = {"uniq", NULL};
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execve(cmd, args, NULL);
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}
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void check_args(int argc, char** argv) {
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if (argc != 2) {
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printf("Usage: %s <filename>\n", argv[0]);
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_exit(1);
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}
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}
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int main(int argc, char** argv) {
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int pfd1[2];
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pipe(pfd1);
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int pid = fork();
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if (pid == 0) {
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run_cat(argv[1], pfd1);
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} else {
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close(pfd1[1]);
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int pfd2[2];
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pipe(pfd2);
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int pid2 = fork();
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if (pid2 == 0) {
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run_sort(pfd1, pfd2);
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} else {
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close(pfd1[0]);
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run_uniq(pfd2);
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}
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}
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}
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