/* this example shows how named pipes may be used */
#define _OPEN_SYS
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>
/* *
* Sample use of mkfifo() *
* */
main()
{ /* start of program */
int flags, ret_value, c_status;
pid_t pid;
size_t n_elements;
char char_ptr[32];
char str[] = "string for fifo ";
char fifoname[] = "temp.fifo";
FILE *rd_stream,*wr_stream;
if ((mkfifo(fifoname,S_IRWXU)) != 0) {
printf("Unable to create a fifo; errno=%d\n",errno);
exit(1); /* Print error message and return */
}
if ((pid = fork()) < 0) {
perror("fork failed");
exit(2);
}
if (pid == (pid_t)0) { /* CHILD process */
/* issue fopen for write end of the fifo */
wr_stream = fopen(fifoname,"w");
if (wr_stream == (FILE *) NULL) {
printf("In child process\n");
printf("fopen returned a NULL, expected valid stream\n");
exit(100);
}
/* perform a write */
n_elements = fwrite(str,1,strlen(str),wr_stream);
if (n_elements != (size_t) strlen(str)) {
printf("Fwrite returned %d, expected %d\n",
(int)n_elements,strlen(str));
exit(101);
}
exit(0); /* return success to parent */
}
else { /* PARENT process */
/* issue fopen for read */
rd_stream = fopen(fifoname,"r");
if (rd_stream == (FILE *) NULL) {
printf("In parent process\n");
printf("fopen returned a NULL, expected valid pointer\n");
exit(2);
}
/* get current flag settings of file */
if ((flags = fcntl(fileno(rd_stream),F_GETFL)) == -1) {
printf("fcntl returned -1 for %s\n",fifoname);
exit(3);
}
/* clear O_NONBLOCK and reset file flags */
flags &= (O_NONBLOCK);
if ((fcntl(fileno(rd_stream),F_SETFL,flags)) == -1) {
printf("\nfcntl returned -1 for %s",fifoname);
exit(4);
}
/* try to read the string */
ret_value = fread(char_ptr,sizeof(char),strlen(str),rd_stream);
if (ret_value != strlen(str)) {
printf("\nFread did not read %d elements as expected ",
strlen(str));
printf("\nret_value is %d ",ret_value);
exit(6);
}
if (strncmp(char_ptr,str,strlen(str))) {
printf("\ncontents of char_ptr are %s ",
char_ptr);
printf("\ncontents of str are %s ",
str);
printf("\nThese should be equal");
exit(7);
}
ret_value = fclose(rd_stream);
if (ret_value != 0) {
printf("\nFclose failed for %s",fifoname);
printf("\nerrno is %d",errno);
exit(8);
}
ret_value = remove(fifoname);
if (ret_value != 0) {
printf("\nremove failed for %s",fifoname);
printf("\nerrno is %d",errno);
exit(9);
}
pid = wait(c_status);
if ((WIFEXITED(c_status) !=0) &&; (WEXITSTATUS(c_status) !=0)) {
printf("\nchild exited with code %d",WEXITSTATUS(c_status));
exit(10);
}
} /* end of else clause */
printf("About to issue exit(0), \
processing completed successfully\n");
exit(0);
}