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1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (c) International Business Machines  Corp., 2001
4  */
5 
6 /*\
7  * [Description]
8  *
9  * Testcase to check if read() successfully sets errno to EAGAIN when read from
10  * a pipe (fifo, opened in O_NONBLOCK mode) without writing to it.
11  */
12 
13 #include <stdio.h>
14 #include <fcntl.h>
15 #include "tst_test.h"
16 
17 static char fifo[100];
18 static int rfd, wfd;
19 
verify_read(void)20 static void verify_read(void)
21 {
22 	int c;
23 
24 	TST_EXP_FAIL(read(rfd, &c, 1), EAGAIN,
25 		     "read() when nothing is written to a pipe");
26 }
27 
setup(void)28 static void setup(void)
29 {
30 	struct stat buf;
31 
32 	sprintf(fifo, "fifo.%d", getpid());
33 
34 	SAFE_MKNOD(fifo, S_IFIFO | 0777, 0);
35 	SAFE_STAT(fifo, &buf);
36 
37 	if ((buf.st_mode & S_IFIFO) == 0)
38 		tst_brk(TBROK, "Mode does not indicate fifo file");
39 
40 	rfd = SAFE_OPEN(fifo, O_RDONLY | O_NONBLOCK);
41 	wfd = SAFE_OPEN(fifo, O_WRONLY | O_NONBLOCK);
42 }
43 
cleanup(void)44 static void cleanup(void)
45 {
46 	SAFE_CLOSE(rfd);
47 	SAFE_CLOSE(wfd);
48 	SAFE_UNLINK(fifo);
49 }
50 
51 static struct tst_test test = {
52 	.needs_tmpdir = 1,
53 	.setup = setup,
54 	.cleanup = cleanup,
55 	.test_all = verify_read,
56 };
57