Question

I included the code below, sorry to bother you with so much code. Argument parsing is ok, i checked it out with watches. I’ve put some printfs to check out where the problem may be and it seems that it doesn’t open the file cat receives as argument. It is called from a shell as “cat -b file“

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

#define TRUE 0
#define FALSE 1

void yes(int argc, char *argv[]);
int cat(int argc, char *argv[]);

//#include "cat.h"
//#include "yes.h"
//#include"tee.h"

char buf[50],c[10], *p2,*p, *pch;

int count;
char *matrix[20];

void yes(int argc, char *argv[])
{
    int i;
// if (argc >= 2 && *argv[1] == '-')
    //  {
    //printf("ERROR!");
    //}
    //if (argc == 1)
    // {
    while (1)
        if (puts("y") == EOF)
        {
            perror("yes");
            exit(FALSE);
        }
    // }

    while (1)
        for (i = 1; i < argc; i++)
            if (fputs(argv[i], stdout) == EOF || putchar(i == argc - 1 ? '\n' : ' ') == EOF)
            {
                perror("yes");
                exit(FALSE);
            }
    //exit(TRUE);
}



int main(int argc, char *argv[])
{
    //p=(char *)malloc(sizeof(char)*50);
    do
    {
        fprintf (stderr, "$ ");
        fgets (buf,50,stdin);
        p=buf;
        fprintf (stderr, "Comanda primita de la tastatura: ");
        fputs (buf, stderr);
        int i=0,j=0;
        //strcpy(p,buf);
        strcpy(c,"\0");
        while (buf[i] == ' ')
        {
            i++;
            p++;
        }
        if (buf[i] == '#')
            fprintf (stderr, "Nici o comanda, ci e un comentariu!\n");
        else
        {
            j=0;
            while (buf[i] != ' ' && buf[i] != '\n')
            {
                i++;
                j++;
            }
            strncpy (c,p,j);
            fprintf (stderr, "%s\n",c);
            if (strcmp (c,"yes") == 0)
            {
                p2 = p+j+1;
                pch = strtok (p2," ");
                count = 0;
                while (pch != NULL)
                {
                    //printf ("%s\n",pch);
                    matrix[count] = strdup(pch);
                    pch = strtok (NULL, " ");
                    count++;
                }
                yes(count, matrix);
                fprintf (stderr, "Aici se va executa comanda yes\n");
            }
            else if (strcmp (c,"cat") == 0)
            {
                p2 = p+j+1;
                pch = strtok (p2," ");
                count = 0;
                while (pch != NULL)
                {
                    //printf ("%s\n",pch);
                    matrix[count] = strdup(pch);
                    pch = strtok (NULL, " ");
                    count++;
                }
                cat(count,matrix);
                fprintf (stderr, "Aici se va executa comanda cat \n");
            }
            else if (strcmp (c,"tee") == 0)
            {
                //tee();
                fprintf(stderr, "Aici se va executa comanda tee\n");
            }


            fprintf (stderr, "Aici se va executa comanda basename\n");

            strcpy(buf,"\0");
        }
    }
    while (strcmp(c, "exit") != 0);
    fprintf (stderr, "Terminat corect!\n");
    return 0;
}
int cat(int argc, char *argv[])
{
    int c ;

    opterr = 0 ;
    optind = 0 ;

    char number = 0;
    char squeeze = 0;
    char marker = 0;

    fprintf(stderr,"SALUT< SUNT IN FUNCTIZE>\n");
    while ((c = getopt (argc, argv, "bnsE")) != -1)
        switch (c)
        {
        case 'b' :
            number = 1;
            break;
        case 'n' :
            number = 2;
            break;
        case 'm' :
            marker = 1;
            break;
        case 's' :
            squeeze = 1;
            break;
        case 'E' :
            marker = 1;
            break;
        }
    if (optind + 1 != argc)
    {
        fprintf (stderr, "\tWrong arguments!\n") ;
        return -1 ;
    }

    FILE * fd = fopen (argv[optind], "r");
    printf("am deschis fisierul %s ",argv[optind]);
    if (fd == NULL)
    {
        printf("FISIER NULL asdasdasdasdasd");
        return 1;
    }

    char line[1025];
    int line_count = 1;

    while (!feof(fd))
    {
        fgets(line, 1025, fd);
        printf("sunt in while :> %s",line);
        int len = strlen(line);
        if (line[len - 1] == '\n')
        {
            if(len - 2 >= 0)
            {
                if(line[len - 2] == '\r')
                {
                    line[len - 2] = '\0';
                    len -= 2;
                }
                else
                {
                    line[len - 1] = '\0';
                    len -= 1;
                }
            }
            else
            {
                line[len - 1] = '\0';
                len -= 1;
            }
        }

        if (squeeze == 1 && len == 0)
            continue;
        if (number == 1)
        {
            fprintf (stdout, "%4d ", line_count);
            line_count++;
        }
        else if (number == 2)
        {
            if (len > 0)
            {
                fprintf (stdout, "%4d ", line_count);
                line_count++;
            }
            else
                fprintf (stdout, "     ");
        }
        fprintf(stdout, "%s", line);
        if (marker == 1)
            fprintf(stdout, "$");
        fprintf(stdout, "\n");
    }

    fclose (fd);

    return 0 ;
}

Answer 1

The problem is that when you are using fgets it includes the newline into the string. Thus when you are passing the file name, it is appended with a \n character which was enter when entering the command. So the file name passed is incorrect. Get ride of the new line maybe on these lines (just a pointer):

char *filename = strtok(argv[optind], "\n");
if( filename == NULL)
{
   /*What the .... */
   Handle error!
}
FILE * fd = fopen (filename, "r");
printf("am deschis fisierul %s ",argv[optind]);
if (fd == NULL)
{
    printf("FISIER NULL asdasdasdasdasd");
    return 1;
}

Hope this helps!

PS: Debugging process
When fopen fails it sets the errno. To get exact error use strerror(errno); or perror. So adding perror("fopen"); in if(fd == NULL) showed fopen : No such file or directory. Next printing the file name as fprintf(stderr, "\n |%s|\n", argv[optind]); showed file name with newline character i.e.

|hello.txt  
|

… then saw fgets. Ah! the new line from there