CODEWITHSUNDEEP
clinuxwindowsunixterminal
JoanaBjatBun
JoanaBjatBun

Reputation: 19

Problems with C program that replicates `cat` command

I made a C program that does what cat command would do, but i ran into a problem. It works well now when adding multiple files as input. Now it doesn't show what was read at stdin, when i don't put any file as a parameter. How can I fix this? 

#include<stdio.h>
#include<fcntl.h>
#include<stdarg.h>
#include<stdlib.h>
#include    "ourhdr.h"
#define BUFFSIZE    8192
int main(int argc,char *argv[])
{
    int fd;
    int n;
    char* index=argv[0];
    char buf[BUFFSIZE];
    if(argc ==1)
    {
        printf("<sintaxa> fisier1 fisier2....\n");
    }
    else
        while(--argc>0)
        {
            if((fd = open(*++argv,O_RDONLY)) == -1)
            {
                printf("%s: %s: No such file or directory\n",index,*argv);
            }
            else
            {
                while((n=read(fd,buf,BUFFSIZE)) > 0)
                    if(write(STDOUT_FILENO,buf,n) != n)
                    {
                        err_sys("write error");
                    }

                if(n<0)
                {
                    err_sys("read error");
                }
                close(fd);
            }
        }

    return 0;
}

Upvotes: 1

Views: 729

Answers (1)

James K. Lowden
James K. Lowden

Reputation: 7837

Use the source, Luke. The NetBSD cat.c implementation (see raw_args function), starts by initializing a local variable to stdin. Then it enters the argv loop unconditionally. If *argv is NULL, the local variable is still set, and it reads from stdin. Else it's overwritten for each argv element.

Upvotes: 1

Related Questions