Segmentation fault (core dumped). Where's the mistake?

[Laycee]

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

int main(int argc, char *argv[])
{
    FILE *file;
    if(argv[1]==NULL) 
        printf("Synopsis: %s output_file\n",argv[0]);
    else
    {
        file = fopen(argv[0],"a+");
        if (file != NULL)
        {
            printf("Error: can't open file\n");
            return 1;
        }
        else
        {
            char *s=malloc(10*sizeof(*s));
            s="^F";
            for (char c = getc(stdin); c != 's'; c = getc(stdin))
                {
                    fputc(c, file );
                }
            free(s);
        }
        fclose(file);
    }
}

[amarantha]

There are several mistakes. First, you're checking if the parameter is set for the program.

if(argv[1]==NULL) 
       ^^^
    printf("Synopsis: %s output_file\n",argv[0]);

And then you try to open your own program file instead of a first-class file.

    file = fopen(argv[0],"a+");
                     ^^^

If the file wasn't open, the function. fopen He'll return the zero index. Therefore, instead of the conditions in this if proposal

    if (file != NULL)
    {
        printf("Error: can't open file\n");
        return 1;
    }

another condition

    if (file == NULL)
    {
        printf("Error: can't open file\n");
        return 1;
    }

Then you've somehow given memory to a symbolic mass.

        char *s=malloc(10*sizeof(*s));

I don't know who's being used anywhere. And now, the index redirects the address of the string literature.

        s="^F";

As a result, you have a memory leak.

And more so in this sentence

free(s);

You're trying to free the memory of a string literature that has a statistical length. Which could also lead to an uncertain programme behaviour.

This cycle

       for (char c = getc(stdin); c != 's'; c = getc(stdin))
            {
                fputc(c, file );
            }

Nor is it correct the function getc may return the value EOFwhich you don't check the cycle.