5 replies to this topic

[erasm]

Im having some trouble implementing this cat emulation program. What would be the best way to go about parsing fp as stdin if no non-option(file args) are parsed through the command line.

pseudo
if(file){
fp = fopen(argv[index])        //as i have
else if(no file args)
fp = stdin;
}
while(c = fgetc(fp) != EOF)
read
}

I'm basically having trouble writing/interpreting this logic.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char *argv[]){
  int optchar;
  int index;
  FILE *fp;
  int lineCount = 1;
  int nflag = 0;
  int sflag = 0;
  int vflag = 0;
  int tflag = 0;
  int c;
  int endline = 1;
  int newlineCount = 0;
  int cntrlFlag = 0;

  while((optchar = getopt (argc, argv, "nsvt")) != -1){
    switch(optchar){
      case 'n':
            nflag = 1;
        break;
      case 's':
            sflag = 1;
        break;
      case 'v':
            vflag = 1;
        break;      
      case 't':
            tflag = 1;
        break;
    }
  }


  for(index = optind; index < argc; index++){
    printf("hi");
    fp = fopen(argv[index], "r");
    printf("index = %d \n", index);
    printf("arg = %s \n", argv[index]);


      if(fp == NULL){
        fprintf(stdout,"File %s couldn't be opened!\n", argv[index]);
        fp = stdin;
      }
        while((c = fgetc(fp)) != EOF){
          cntrlFlag = 0;
          if(c != '\n'){
            newlineCount = 0;
          }
          if(nflag && endline){
            if(sflag && newlineCount < 2){
              printf("%5d  ", lineCount);
              lineCount++;
            }
            if(!sflag){
              printf("%5d  ", lineCount);
              lineCount++;
            }
            endline = 0;
          }
          if(iscntrl(c) && tflag && c != '\n'){
            c += 64;
            printf("^%c", c);
            cntrlFlag = 1;
          }
          if(newlineCount < 2 && sflag && !cntrlFlag){
            printf("%c", c);
          }
          if(!sflag && !cntrlFlag){
            printf("%c", c);
          }
          if(c == '\n'){
            endline = 1;
            newlineCount++;
          }
        }
    fclose(fp);
  }
  return 0;
}

Edited by Jaan, 11 August 2009 - 03:32 AM.

[WingedPanther]

stdin will never return EOF. You will need some other sentinel value for it. The ASCII value of Ctrl-Z might be one option.

[G_Morgan]

Ctrl+Z on Windows gives EOF AFAIK. Also Ctrl+D on Unix systems.

[dargueta]

Quote

Also Ctrl+D on Unix systems.

Not necessarily; you can disable that with your cshrc/bashrc file. I would also stick in a CTRL-C handler, as that's a more or less universal way of telling the program to stop.

[Chinmoy]

ctrl+D is different from ctrl+c.
check this page : [SOLVED] Difference bw ctrl C & ctrl D & ctrl Z - Linux Forums

It says ctrl+c, ctrl+d and ctrl+z are all different.

[dargueta]

I know they're different. But you can't override CTRL-C functionality on a command prompt, only in your program. Hence my "more or less universal" comment. They may send different signals, but CTRL-C and CTRL-D accomplish the same thing in the end. CTRL-Z is a special case, because on Windows systems it sends EOF like G_Morgan said, and on Linux (probably UNIX as well) it tells the shell to suspend the current process, but not kill it. AFAIK you can't override that either. Think of it this way: CTRL-C sends SIGINT on Windows and *NIX. It would do you well to stick in a handler for it at the very least. CTRL-D and CTRL-Z could get messy on Windows.