78 lines
2.0 KiB
C
78 lines
2.0 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/*
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* This program uses nonblocking I/O to write 50 megabytes of data to
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* its standard output, reporting on standard error the number of bytes
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* written by each system call. If standard output is a pipe or network,
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* connection, we may observe that some write system calls "fail", because
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* buffers are full, or flow-control has been applied; this is normal.
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#define BUFSIZE 1024000
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int
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main(int argc, char **argv) {
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int flags, count, loops, num;
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char buf[BUFSIZE], *ptr;
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(void)argv;
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/* fill buffer with 'a' */
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memset(buf, 'a', BUFSIZE);
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if ((flags = fcntl(STDOUT_FILENO, F_GETFL, 0)) < 0) {
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perror("getting file flags");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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if (argc > 1) {
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/* set non-blocking mode on stdout */
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if (fcntl(STDOUT_FILENO, F_SETFL, flags|O_NONBLOCK) < 0) {
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perror("setting file flags");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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}
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for (loops = 0; loops < 50; loops++) {
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ptr = buf;
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num = BUFSIZE;
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while(num > 0) {
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count = write(STDOUT_FILENO, ptr, num);
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if (count >= 0) {
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ptr += count;
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num -= count;
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(void)fprintf(stderr, "wrote %d bytes\n", count);
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} else {
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(void)fprintf(stderr, "write error: %s\n",
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strerror(errno));
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}
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}
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}
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/* set file flags back as they were; not strictly necessary, since
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* we exit right away, but illustrative of good practice */
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(void)fcntl(STDOUT_FILENO, F_SETFL, flags);
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exit(EXIT_SUCCESS);
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}
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