I want to use fgets instead of fscanf to get stdin and send it to a child process via a pipe. The code below works for sorting the lines in the file but replacing
fscanf(stdin, "%s", word)
with
fgets(word, 5000, stdin)
gives me the warning
warning: comparison between pointer and integer [enabled by default]
Otherwise the program seems to work. Any ideas why I am getting the warning?
int main(int argc, char *argv[])
{
pid_t sortPid;
int status;
FILE *writeToChild;
char word[5000];
int count = 1;
int sortFds[2];
pipe(sortFds);
switch (sortPid = fork()) {
case 0: //this is the child process
close(sortFds[1]); //close the write end of the pipe
dup(sortFds[0]);
close(sortFds[0]);
execl("/usr/bin/sort", "sort", (char *) 0);
perror("execl of sort failed");
exit(EXIT_FAILURE);
case -1: //failure to fork case
perror("Could not create child");
exit(EXIT_FAILURE);
default: //this is the parent process
close(sortFds[0]); //close the read end of the pipe
writeToChild = fdopen(sortFds[1], "w");
break;
}
if (writeToChild != 0) { //do this if you are the parent
while (fscanf(stdin, "%s", word) != EOF) {
fprintf(writeToChild, "%s %d\n", word, count);
}
}
fclose(writeToChild);
wait(&status);
return 0;
}
fscanf returns an int
, fgets a char *
. Your comparision with EOF results in the warning for a char *
since EOF is an int
.
fgets returns NULL on EOF or error, so check for that.