How to get string of unknown length in C?

Question

I have been trying to learn C, and was wondering: how would one get a string with an unknown length in C? I have found some results, but am not sure how to apply them.

C has char arrays, you should declare char array based on length of the string. — Marios Nikolaou, Apr 11 '19 at 21:05
Assuming you are asking about user input - you can read char by char (or by length limited chunks) in a loop and dynamically allocate/reallocate space to store it. — Eugene Sh., Apr 11 '19 at 21:09
Which results have you found? How did you try to apply them? What was the problem with applying them? Where's the code — an MCVE ([MCVE]) — that shows the problem you're having applying what you think is the best solution? — Jonathan Leffler, Apr 11 '19 at 21:14
Not sure why anyone voted this as "unclear what you're asking", it seems very clear to me — M.M, Apr 12 '19 at 02:33

score 0 · Accepted Answer · answered Apr 11 '19 at 21:18

If you're ok with extensions to the Standard, try POSIX getline().

Example from documentation:

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

int main(void)
{
    FILE *fp;
    char *line = NULL;
    size_t len = 0;
    ssize_t read;
    fp = fopen("/etc/motd", "r");
    if (fp == NULL)
        exit(1);
    while ((read = getline(&line, &len, fp)) != -1) {
        printf("Retrieved line of length %zu :\n", read);
        printf("%s", line);
    }
    if (ferror(fp)) {
        /* handle error */
    }
    free(line);
    fclose(fp);
    return 0;
}

Ok, I'll check this out! Thanks! – nerdguy Apr 11 '19 at 22:27 — nerdguy, Apr 11 '19 at 22:27

How to get string of unknown length in C?

1 Answers1