Thread: find .c in a string

Start by writing a program that prints its command line arguments. Compile and test, fixing it until it works.

Modify the program to print only those command line arguments that end with ".c". Compile and test, fixing it until it works.

Modify the program to change the ".c" ending part of each such command line argument to ".o" and print the result. Compile and test, fixing it until it works.

You're done.

You can take help of functions like strtok() (strtok_r() if working with multi-threaded application), sprintf().

Originally Posted by maven

You can take help of functions like strtok() (strtok_r() if working with multi-threaded application)

There should be no need to use strtok. Rather than tokenise based on ".", just examine the last two characters of each command line argument, if the string has at least 2 characters.

Well I did that, and I am sure it is not what you expected me to do knowing that it doesn't work...

Code:

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

int main (int argc, char*argv[]){
    int i;
    int lenth;
    char argx[100];
    int nbarg;
    for (i=1;i<argc;i++){
        strcpy(argx, argv[i]);
        lenth = strlen(argv[i]);
        if (argx[lenth]=="c"&& argx[(lenth-1)]== ".") {
            printf("%s ",argv[i]);
            }
        }
        printf("\n");
    return 0;
    }

Code:

questionB1.c: In function ‘main’:
questionB1.c:12:18: warning: comparison between pointer and integer [enabled by default]
questionB1.c:12:41: warning: comparison between pointer and integer [enabled by default]

well maybe itwill sound really nooby but seeing that i tryed strcmp(argx[lenth],"c")==0 but it is even worse...

I use strcpy because i didn't want to to argv[i][lenth] which would have been a 2 dimentions table...

argx[lenth] is wrong: an array with lenth elements has a largest index of lenth-1. You should be comparing with argx[lenth-1] and argx[lenth-2] instead. Furthermore, you are comparing with characters, so it should be 'c' and '.', not "c" and ".". Plus, consider what happens if a command line argument consists of just one character.

Oh, you don't need the argx array as you can use argv directly, and "lenth" should really be "length".

EDIT:

Originally Posted by dekl

I use strcpy because i didn't want to to argv[i][lenth] which would have been a 2 dimentions table...

If you want to avoid that, all you need is:

Code:

char *argx;

Then in the loop:

Code:

argx = argv[i];

Refer to my edit.

Originally Posted by dekl

what is strcpy for ?

When you really need to copy an entire string to an array that has enough space to hold it.

Originally Posted by dekl

here is the final working program!

Good, but your indentation is slightly misleading. I might indent it as:

Code:

#include <stdio.h>
#include <string.h>
  
int main(int argc, char *argv[]) {
    int i, j;
    int length;
    char *argx;
    for (i = 1; i < argc; i++) {
        argx = argv[i];
        length = strlen(argv[i]);
        if (argx[length-1] == 'c' && argx[(length - 2)] == '.') {
            for (j = 0; j < (length-1); j++) {
                printf("%c", argx[j]);
            }
            printf("o ");
        }
    }
    printf("\n");
    return 0;
}

Now, you should check that the length >= 2 before you start comparing characters. Then, you don't need that inner loop; you just need to change the last character to a 'o' once you know the string ends with ".c". After that, you can print the string with just a single printf.