Thread: command line arguments using argc and argv.

hello all,
I am trying to write a program where I can read info from a data file into my program and write info to another data file using argc and argv functions.
this is what i have so far and am not sure it is correct.

main( int argc, char* argv[] )
{
char record [37];
int i;
FILE *input;
FILE *output;
input=fopen(argv[1],"r");
output=fopen(argv[2],"w");

printf("Number of files to be printed: %i\n", argc -1);

for (i=1; i<argc; i++)
{
printf("\n\tFile:\t%s\n",argv[i]);
input=fopen(argv[i],"r");

while (fgets(record,37,input) != NULL)
printf("%s",record);

fclose(input);
fclose(output);
}
return(0);
}

(ps my input file has about 30 characters in it on 4 seperate lines).

Any input from any of you guys would be much appreciated, as I dont think this code I wrote is completely correct.
thank you

>input=fopen(argv[1],"r");
>output=fopen(argv[2],"w");
This really doesn't do too much. The first thing you do is reassign input to another return from fopen, and you never use output except to break the program by fclosing it multiple times.

It looks like you want to write your own version of cat:

Code:

#include <stdio.h>

int main(int argc, char *argv[])
{
  char buffer[BUFSIZ];

  if (argc < 2) {
    /* No input files, take input from stdin */
    while (fgets(buffer, sizeof buffer, stdin) != NULL)
      fputs(buffer, stdout);
  }
  else {
    FILE *in;
    int i;

    for (i = 1; i < argc; i++) {
      if ((in = fopen(argv[i], "r"))== NULL)
        continue;

      while (fgets(buffer, sizeof buffer, in) != NULL)
        fputs(buffer, stdout);
    }
  }

  return 0;
}

Of course, getting the basic functionality to work isn't the fun part. The fun part is adding all of the switch handling and nifty options that cat supports.