Redirecting

Applications Programming
1

How to redirect the contents of a file to a command?

The contents of the file are the arguments necessary for the command.

thx in advance.

bye
svh

2

This may be kind of cheating, but:

include <stdlib.h>

int main(int argc, char *argv[])
{
  return(system("./some-program `cat filename`"));
}

Or if you must do it from C alone, look into the execvp family of functions.

3

I will try it out

thx,
bye

4

well, above c program will do absolutely nothing.
if your shell script code is

./prog < file

then you can try this:

#include <stdio.h>

int main()
{
    int c;

    while( (c = fgetc(stdin)) != EOF )
    {
        /* do something with input char */
    }
}
5

Considering I actually wrote it and tested it before posting here, I think that pronouncement is premature. I'm presuming he means arguments when he says arguments, not stdin.

6

Or you can use Shell's "Here Documents" if you wanna put your command in the same place as your data on which that command will act.

$cat findpattern.sh
grep 'pattern' <<End # Here document tag
Hi here is pattern
Pattern here, but escape from grep
No grep in this line
Can't find here
Pattern here again
pattern here
End # Here document tag

$./findpattern.sh
Hi here is pattern
pattern here