Try It Yourself - SyntaxStudy Editor

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

/* Read entire file into a malloc\'d buffer (caller must free) */
char *read_file(const char *path, long *out_size)
{
    char *buf  = NULL;
    FILE *f    = NULL;
    long  size = 0;

f = fopen(path, "rb");
    if (!f) {
        fprintf(stderr, "fopen '%s': %s
", path, strerror(errno));
        goto done;
    }

if (fseek(f, 0, SEEK_END) != 0) { perror("fseek"); goto done; }
    size = ftell(f);
    if (size < 0)                   { perror("ftell"); goto done; }
    rewind(f);

buf = malloc((size_t)size + 1);
    if (!buf)                       { perror("malloc"); goto done; }

size_t got = fread(buf, 1, (size_t)size, f);
    if ((long)got != size && ferror(f)) {
        perror("fread");
        free(buf);
        buf = NULL;
        goto done;
    }
    buf[got] = '\0';   /* null-terminate for text use */
    if (out_size) *out_size = (long)got;

done:
    if (f) fclose(f);
    return buf;
}

int main(void)
{
    /* Write a test file first */
    FILE *f = fopen("test.txt", "w");
    if (f) {
        fprintf(f, "Line one
Line two
Line three
");
        fclose(f);
    }

long sz;
    char *content = read_file("test.txt", &sz);
    if (content) {
        printf("Read %ld bytes:
%s
", sz, content);
        free(content);
    }

/* Demonstrate error path */
    char *missing = read_file("no_such_file.txt", NULL);
    if (!missing) printf("Correctly handled missing file.
");

return EXIT_SUCCESS;
}