59 lines
1.2 KiB
C
59 lines
1.2 KiB
C
#define _GNU_SOURCE
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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// You may assume that lines are no longer than 1024 bytes
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#define LINELEN 1024
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static void usage (void) __attribute__ ((unused));
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int
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main (int argc, char *argv[])
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{
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int opt;
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int n = 5;
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while ((opt = getopt (argc, argv, "n:")) != -1)
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{
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switch (opt)
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{
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case 'n':
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n = strtol (optarg, NULL, 10);
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break;
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default:
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printf ("./bin/head: invalid option -- \'%c\'\n", optopt);
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exit (EXIT_FAILURE);
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}
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}
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FILE *file = optind < argc ? fopen (argv[optind], "r") : stdin;
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if (file == NULL)
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{
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perror ("Failed to open input file");
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exit (EXIT_FAILURE);
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}
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char buffer[LINELEN];
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int count = 0;
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while (count < n && fgets (buffer, sizeof (buffer), file) != NULL)
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{
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printf ("%s", buffer);
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count++;
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}
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return EXIT_SUCCESS;
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}
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static void
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usage (void)
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{
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printf ("head, prints the first few lines of a file\n");
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printf ("usage: head [FLAG] FILE\n");
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printf ("FLAG can be:\n");
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printf (" -n N show the first N lines (default 5)\n");
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printf ("If no FILE specified, read from STDIN\n");
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}
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