Segmentation error

[sagarbsa]

Hii,
when I run this program using GCC there is no compilation error but I get segmentation error. Please help me

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

int main()
{
FILE *fp;
char *filename();

if ((fp = fopen (filename(),"r" )) == NULL)

{
printf ("File could not be opened\n");
// error_handler() ;
}
else
{
printf ("file opened");
}
}

char *filename() /* return filename */

{ static char *filenm = ".............. ..........";

do
{
printf ("Enter filename :");
scanf ("%24s",&filenm );
// skipgarb();
}
while (strlen(filenm) == 0);
return (filenm);
}

[Savage]

Well,here is your problem:

[CODE="cpp"]char *filename() /* return filename */

{ static char *filenm = ".............. ..........";

do
{
printf ("Enter filename :");
scanf ("%24s",&filenm );
// skipgarb();
}
while (strlen(filenm) == 0);
return (filenm);[/CODE]

You have assigned to filenm a literal string,so it's now pointing to it,then you decide to change that string to other which is probably longer,and there you go,my favorite segmentation error.

A single question,why is filenm static?

PS:please use code tags(#button)
Savage

[sagarbsa]

Thanks for the reply. But i am still not getting the output. I added the skipgarb function also. And I am using only a file name of 6 character "myfile". The program is as follows.

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

int main()
{
FILE *fp;
char *filename();

if ((fp = fopen (filename(),"r" )) == NULL)

{
printf ("File could not be opened\n");
// error_handler() ;
}
else
{
printf ("file opened");
}
}

char *filename() /* return filename */

{ static char *filenm = ".............. ..........";

do
{
printf ("Enter filename :");
scanf ("%24s",&filenm );
skipgarb();
}
while (strlen(filenm) == 0);
return (filenm);
}

skipgarb() /* skip garbage corrupting scanf */

{
while (getchar() != '\n')
{
}
}

The error which I get is as follows. Help.

[sagar@localhost ~]$ gcc fileopp4.c
[sagar@localhost ~]$ ./a.out
Enter filename :myfile
Segmentation fault
[sagar@localhost ~]$

[Savage]

Try using gets instead of scanf.

Savage

[sagarbsa]

No Better Luck. Same Error.

[Savage]

No Better Luck. Same Error.

It looks like that this happens because filename is a pointer,change it to stack array and it will work.

Savage

[Savage]

It looks like that this happens because filename is a pointer,change it to stack array and it will work.

Savage

You can get it to work with pointer also,but you must first initialize pointer to a valid address.

Savage

[sagarbsa]

Hii thanks for your reply. I modified the program for better debugging and is as follows.
#include<stdio. h>
#include<string .h>
#include<stdio. h>
#include<string .h>

int main()
{
#include<stdio. h>
#include<string .h>

char *filename() /* return filename */

{
static char *filenm = ".............. ..........";
printf("Entered the *file function\n");
do
{
printf ("Enter filename :");
scanf ("%24s",filenm) ;
printf("Took file name\n");
skipgarb();
}
while (strlen(filenm) == 0);
return (filenm);
}

skipgarb() /* Skip input garbage corrupting scanf */
{
while (getchar() != '\n');
printf("Finishe d skipgarb func");
}

int main()
{
FILE *fp;
char *filename();

if ((fp = fopen (filename(),"r" )) == NULL)

{
printf ("File could not be opened\n");
}
else
{
printf ("File opened\n");
fclose (fp);
printf("File closed sucessfully");
}

}

Then when I ran the program the result is as follows.So the error is in the function where we enter the filename as it doent print the line "took file name". Give your suggestions. Tried gets also.

[sagar@localhost cprogfiles]$ ./a.out
Entered the *file function
Enter filename :myfile
Segmentation fault

[Savage]

Read my previous two posts.

Savage

[weaknessforcats]

static char *filenm = ".............. ..........";

Have you considered that filenm is a literal and that makes it const??? You cannot change the value of a literal.

Just create an array:
[code=c]
static char filenm[] = ".............. ..........";
[/code]

and things will start working.

[dharmarajat]

Have you considered that filenm is a literal and that makes it const??? You cannot change the value of a literal.

Just create an array:
[code=c]
static char filenm[] = ".............. ..........";
[/code]

and things will start working.

(or)

just allocate memmory to get the input file name and point the poiter to the memmory, as

static char *filenm;
filenm = (char *)malloc(24);
scanf ("%24s",filenm) ;

it works...

[JosAH]

(or)

just allocate memmory to get the input file name and point the poiter to the memmory, as

static char *filenm;
filenm = (char *)malloc(24);
scanf ("%24s",filenm) ;

it works...

*ahem* this thread has been dead for about a year. No need to resurrect it.

kind regards,

Jos