60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
/*
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* cat_nonblock.c - open a file and display its contents, but exit rather than
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* wait for input.
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*/
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#include <errno.h> /* for errno */
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#include <fcntl.h> /* for open */
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#include <stdio.h> /* standard I/O */
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#include <stdlib.h> /* for exit */
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#include <unistd.h> /* for read */
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#define MAX_BYTES 1024 * 4
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int 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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puts(errno == EAGAIN ? "Open would block" : "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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/* 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 (int 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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return 0;
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}
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