mirror of https://github.com/tLDP/LDP
69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
/* cat_noblock.c - open a file and display its contents, but exit rather than
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* wait for input */
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/* Copyright (C) 1998 by Ori Pomerantz */
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#include <stdio.h> /* standard I/O */
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#include <fcntl.h> /* for open */
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#include <unistd.h> /* for read */
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#include <stdlib.h> /* for exit */
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#include <errno.h> /* for errno */
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#define MAX_BYTES 1024*4
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main(int argc, char *argv[])
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{
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int fd; /* The file descriptor for the file to read */
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size_t bytes; /* The number of bytes read */
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char buffer[MAX_BYTES]; /* The buffer for the bytes */
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/* Usage */
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if (argc != 2) {
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printf("Usage: %s <filename>\n", argv[0]);
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puts("Reads the content of a file, but doesn't wait for input");
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exit(-1);
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}
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/* Open the file for reading in non blocking mode */
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fd = open(argv[1], O_RDONLY | O_NONBLOCK);
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/* If open failed */
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if (fd == -1) {
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if (errno = EAGAIN)
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puts("Open would block");
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else
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puts("Open failed");
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exit(-1);
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}
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/* Read the file and output its contents */
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do {
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int i;
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/* Read characters from the file */
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bytes = read(fd, buffer, MAX_BYTES);
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/* If there's an error, report it and die */
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if (bytes == -1) {
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if (errno = EAGAIN)
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puts("Normally I'd block, but you told me not to");
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else
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puts("Another read error");
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exit(-1);
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}
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/* Print the characters */
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if (bytes > 0) {
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for(i=0; i<bytes; i++)
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putchar(buffer[i]);
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}
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/* While there are no errors and the file isn't over */
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} while (bytes > 0);
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}
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