Chose To write a File to a Specific Directory

Question

So I'm trying to create a file and save it to a desired directory.

eg: user-input:

Directory? c:\user\sample\

Name? hello.txt

This is what I've tried so far:

char str[200],str2[200];
FILE * out_file;
fgets(str,sizeof str,out_file);
fgets(str2,sizeof str2,out_file);
out_file = fopen(str+str2,"w");

Can someone please help me with this issue?

You cannot concatenate strings with the `+` operator in C. Use `strcat` or any other appropriate function for this purpose. — fuz, Jan 20 '16 at 12:05
As, @FUZxxl said, you will have to use `strcat` to concatenate the strings. — Box Box Box Box, Jan 20 '16 at 12:06
Read this [How to concatenate 2 strings in C?](http://stackoverflow.com/questions/8465006/how-to-concatenate-2-strings-in-c) — mazhar islam, Jan 20 '16 at 12:08
You should have at least reported which kind of error you had, i.e. at compile time (which error?) or runtime (which wrong behaviour?) — Antonio, Jan 20 '16 at 13:15

Danny_ds · Answer 1 · 2016-01-20T13:06:47.423

1

A few issues:

You'll have to use strcat() to concatenate the strings.

Here you are reading from out_file before opening it.

fgets(str,sizeof str,out_file);
fgets(str2,sizeof str2,out_file);

A quick example (no error checking done):

char str[200], str2[200];
char fname[400];
FILE *out_file;

printf("\nEnter path: ");
scanf("%199s", str);  
printf("\nEnter filename: ");
scanf("%199s", str2);

strcpy(fname, str);
strcat(fname, str2);

out_file = fopen(fname, "w");

Or, a shorter way:

char str[400],str2[200];
FILE * out_file;

printf("\nEnter path: ");
scanf("%199s", str);  
printf("\nEnter filename: ");
scanf("%199s", str2);

strcat(str, str2);

out_file = fopen(str, "r");

edited Jan 20 '16 at 13:06

answered Jan 20 '16 at 12:08

Danny_ds

11,201
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Never use `gets`. Use `fgets`. – Box Box Box Box Jan 20 '16 at 12:36
`gets` is very much dangerous. Check this out: [Why is the gets function so dangerous that it should not be used?](http://stackoverflow.com/questions/1694036/why-is-the-gets-function-so-dangerous-that-it-should-not-be-used). – Box Box Box Box Jan 20 '16 at 12:37
@AshishAhuja - Yes, but wanted to keep the sample short (newlines etc.) - Used `scanf()` instead. – Danny_ds Jan 20 '16 at 13:08

score 1 · Answer 2 · edited May 23 '17 at 10:29

See How to concatenate 2 strings in C?.

Also, you should use strcat.

Check out this tutorial.

An example in this is:

/* Example using strcat by TechOnTheNet.com */

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

int main(int argc, const char * argv[])
{
   /* Define a temporary variable */
   char example[100];

   /* Copy the first string into the variable */
   strcpy(example, "TechOnTheNet.com ");

   /* Concatenate the following two strings to the end of the first one */
   strcat(example, "is over 10 ");
   strcat(example, "years old.");

   /* Display the concatenated strings */
   printf("%s\n", example);

   return 0;
}

In your case it would be:

char file_name[200 + 200];
file_name [0] = '\0'                    // To make sure that it's a valid string.

strcpy (file_name, str);                // Concatenate `str` and `file_name`
strcat(file_name, str2);                // Concatenate `str2` and `file_name`

out_file = fopen(file_name, "w");       // Open the file.

Also, thanks to 'laerne' for pointing out some mistakes.

You should initialize `file_name[0] = '\0'` to make sure it's a valid empty string. Or copy the first string entirely with `strcpy`. — Lærne, Jan 20 '16 at 12:23

ForceBru · Answer 3 · 2016-01-20T12:11:36.917

0

You cannot concatenate strings like this in C! *

You'd better use strcat:

char fname[200+200];

strcat(fname, str);
strcat(fname, str2);

out_file = fopen(fname, "w");

_{* Although you are allowed to add pointers. In your case it doesn't do what you expect.}

edited Jan 20 '16 at 12:11

answered Jan 20 '16 at 12:06

ForceBru

43,482
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Chose To write a File to a Specific Directory

3 Answers3