CODEWITHSUNDEEP
cpipe
Hovestar
Hovestar

Reputation: 1627

C read contents of file piped in

I'm trying to do analysis on some data and I am building a few tools that I was hoping to chain together with pipes.

cat file.dat | ./tool | ./tool2 ...

But I'm not sure how to read the piped in data. I know it's coming in through stdin, but I can exactly wait for the file end. So I guess I'm looking for something like this:

long value;
while(scanf("%ld\n",&value)){
  value2 = do_something(value);
  printf("%ld\n",value2);
}
return 0;

But scanf, doesn't return 0 when stdin is "empty" what is the proper way to do this?

Upvotes: 0

Views: 71

Answers (1)

Lukáš Lalinský
Lukáš Lalinský

Reputation: 41306

The function scanf returns EOF when it reaches the end of file. You can use a code like this to check for that:

while (1) {
    long value;
    int ret = scanf("%ld\n", &value);
    if (ret == EOF) {
        break;
    }
    printf("%ld\n", value);
}

See the docs for more details.

Upvotes: 1

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