Ttykuu

I wrote my own implementation of the linux cat command in C for my computer laboratory class. We were asked to replicate its functionality with no options passed as arguments or with just the -b, -n and -s options.

I'm posting the code here because, although it works fine, i feel a little bit insecure about. Firstly because i think i "over-coded" it a bit, specially on the option handling part, and also, because i'm still not very confortable working with pointers and so i am not very sure if my approach does not generate memory leaks or malfunctions.

Here it is:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#define BUF_SIZE 1024

int readStdin(int index, int bflag, int nflag)
 char buffer[BUF_SIZE];
 while(fgets(buffer, BUF_SIZE, stdin)) //reads from the standard input and prints the input
 if (nflag)
 printf(" %d %s", index, buffer);
 index++;
 
 if (bflag)
 if (*buffer == 'n')
 printf ("%s", buffer);
 
 else
 printf (" %d %s", index, buffer);
 index++;
 
 
 else 
 printf("%s", buffer);
 
 
 return index; //returns the incremented index to perpetuate its use


int readFile(char* filename, FILE* fp, int index, int bflag, int nflag)
 char ch;
 char s[BUF_SIZE];
 if (fp==NULL) //in case the file doesn't exist
 printf("%s: No such file or directoryn", filename);
 exit(1);
 

 if (bflag)
 while ((fgets(s,BUF_SIZE,fp)))
 if (strcmp(s,"n") == 0)
 printf (" %s", s);
 
 else 
 printf (" %d %s", index, s);
 index++;
 
 
 fclose(fp);
 
 if (nflag)
 while ((fgets(s,BUF_SIZE,fp)))
 printf (" %d %s", index, s);
 index++;
 
 fclose(fp);
 
 else
 while ((ch=fgetc(fp)) != EOF) //printing loop
 putchar(ch);
 
 fclose(fp);
 
 return index;


void readArgs(int argc, char* argv[])
 FILE* fp;
 int index = 1; //line index. to be used in case -b or -n is passed as an argument
 int option; //option passed as argument
 int bflag = 0; //-b option deactivated by default
 int nflag = 0; //-n option deactivated by default
 opterr = 0; //deactivates getopt's default error messages

 //checks if there are options passed as argument and updates their flags
 while ((option = getopt(argc, argv, "bn")) != -1)
 switch (option)
 case 'b':
 bflag = 1;
 break;
 case 'n':
 nflag = 1;
 break;
 case '?': //in case there was some problem
 exit(1);
 
 

 if (bflag == 1 && nflag == 1) //if -b and -n are passed as argument, b overrides n
 nflag = 0;
 

 for (int i=optind; i<argc; i++)
 if (*argv[i] == '-') //in case of '-' in argv[i], reads from stdin and prints
 index = readStdin(index, bflag, nflag);
 clearerr(stdin);
 
 else //prints the contents of the file in *argv[i]
 fp = fopen(argv[i], "r");
 index = readFile(argv[i], fp, index, bflag, nflag);
 
 


int main(int argc, char* argv[])
 if (argc<2) //if there are no arguments
 readStdin(1,0,0);
 return 0;
 
 readArgs(argc, argv); //otherwise
 return 0;

I didn't implement the -s option because i cant think of a way to handle it at the same time as the other options. That's why i think that the way i am handling the options part is a bit inefficient.

Any suggestions?