CODEWITHSUNDEEP
c
RTC222
RTC222

Reputation: 2323

Format error with sprintf to create file name buffer

I am using sprintf to format a file name buffer, but clang-10 reports:

warning: format specifies type 'int' but the argument has type 'char *' [-Wformat] sprintf(file_name_buffer, "%c", file_name);

This is the code:

char file_name[ ] = "/path/filename.bin";
int file_name_len = sizeof(file_name);
char file_name_buffer[file_name_len];
sprintf(file_name_buffer, "%c", file_name);
outfile = fopen(file_name_buffer, "wb+");

I thought %c is the format string for a char string. How do I format this for sprintf ?

Thanks

Upvotes: 0

Views: 60

Answers (1)

Ted Lyngmo
Ted Lyngmo

Reputation: 117298

%c is for a single char and %s is for strings.

#include <stdio.h>

int main(void) {
    char file_name[] = "/path/filename.bin";
    int file_name_len = sizeof(file_name);
    char file_name_buffer[file_name_len];

    sprintf(file_name_buffer, "%s", file_name);
//                             ^^

    FILE *outfile = fopen(file_name_buffer, "wb+");
    if(outfile) {
        // success
    } else {
        // failure
    }
}

In this case, you may want to use strncpy instead of sprintf though since there's not much of formatting going on in your sprintf.

#include <string.h>

//...

strncpy(file_name_buffer, file_name, sizeof file_name_buffer);

Upvotes: 2

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