Appending "

Hi all,

I have a string and I want to append (") at the beginning and the end of it to get:

"String.....".

This is my program which works fine but it needs "(s) ( becuase the required command is: cygpath -w "string").

Code:

---

void converter( char *cyg, char *win)
{
FILE *fp;

char command[1000] = "cygpath -w ";

strcat( command, cyg);

fp = popen(command, "r");

if (fp == NULL)
{
  printf("Error in opening pipe");
  exit(1);
}

while(fgets(win, 1000, fp) != NULL)

if (pclose(fp) == -1)
{
  printf("Error is countered in closing the pipe ");
}

}

---

If there is any unlogical implementation in the code, please let me know.

Wait your help.

You could malloc() a new string large enough to hold the current one plus the quotation marks, and copy the string over.

Otherwise, you'd have to shift the entire string over to make room for the first quotation mark.

Can't I append the first " before storing anything in the buffer, and then starts buffering after this and at the end appending the second "?

Mmm, yes, you can do that.

If you don't need the string for anything else, that's the best way of doing it.

okay, then I tried this approach and I failed :( can you please look at the code and help me.

char command[1000] = "cygpath -w \"";

strcat( command, cyg);

strcat( command, "\"");

okay, how this can be done for "win" ? The second " can be added using strcat, but what about the first " ?

This seems to work and its doing what vart suggested.

Code:

---

#include <stdio.h>
#include <string.h>
#define size 100

int main()
{
    char command[size] = "cygpath -w \""; // <- first " is added here
    char string[size];
   
    fgets(string, size, stdin);
    string[strlen(string)-1]='\0';
   
    strcat( command, string);

    strcat( command, "\"");
   
    printf("%s", command);
    getchar();
}

---

How about:

Code:

---

#include <stdio.h>
#include <string.h>
#define size 100

int main()
{
    char command[size];
    char string[size];
   
    fgets(string, size, stdin);
    snprintf(command, size, "cygpath -w \"&#37;s\"", string);
   
    printf("%s\n", command);
    getchar();
}

---

Not the safest, but yeah it should work most of the time. You take a slight chance on overrunning your buffer, which might not be a problem I guess since command and string are next to each other on the stack......

fgets and snprintf - both check the array bounds, so where do you see the problem of buffer overrun?

The problem here - is the \n char that should be removed from the strings after fgets

Nope, I'm confusing myself. brewbuck is right. Apologies yet again (I really need to stop this. :) ).

It'll work, but you'll truncate the command from string if the length is too large. Not really a major problem.

Quote:

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Originally Posted by vart

The problem here - is the \n char that should be removed from the strings after fgets

---

Ehh, yeah. Forgot about that, as I usually do. It's simple to write a function that strips that off.

Quote:

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Originally Posted by vart

fgets and snprintf - both check the array bounds, so where do you see the problem of buffer overrun?

---

This sounds like you can get can get a buffer overflow by putting a big string into a printf(). I guess I'll have a look at what snprintf() does different then.

What I mistakenly thought was happening was that we were writing at an offset of command, but passing the size size, which could result in a buffer overrun.

We should be safe with this.

Incidentally, printf() is almost always always safe if you use it right. sprintf() just uses a printf()-sorta-means to write to a string. snprintf() does it safely.

The only problem with it - it is not so portable, for example on MS compiler you have

Quote:

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Routine - Required Header - Compatibility
_snprintf - <stdio.h> - Win 95, Win NT

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instead