getline, getwline, getdelim, getwdelim - cppreference.com

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# getline, getwline, getdelim, getwdelim

From cppreference.com
< c‎ | experimental‎ | dynamic

Defined in header `<stdio.h>` |  |
ssize_t getline(char **lineptr, size_t *n, FILE *stream); | (1) | (dynamic memory TR)
ssize_t getwline(wchar_t **lineptr, size_t *n, FILE *stream); | (2) | (dynamic memory TR)
ssize_t getdelim(char ** restrict lineptr, size_t * restrict n, int delimiter, FILE *stream); | (3) | (dynamic memory TR)
ssize_t getwdelim(wchar_t ** restrict lineptr, size_t * restrict n, wint_t delimiter, FILE * stream); | (4) | (dynamic memory TR)

1) Behaves like getdelim(lineptr, n, '\n', stream)
2) Behaves like getwdelim(lineptr, n, L'\n', stream)
3) Reads from the stream `stream` as if by fgetc, until `delimiter` is encountered, storing the characters in the buffer of size `*n` pointed to by `*lineptr`, automatically increasing its size as if by realloc to fit the entire input, including the delimiter, and adding a null terminator. `*lineptr` may be null, in which case `*n` is ignored and `getline` allocates a new buffer as if by malloc. The behavior is undefined if `delimiter` has a value that is outside the range of `unsigned char` or EOF.
4) Same as (3), except the characters are read as if by fgetwc and that `delimiter` must be a valid `wchar_t` or WEOF.

If `*lineptr` is not null, the behavior is undefined if `*lineptr` is not a pointer that can be passed to free or if `*n` is less than the size of the allocated memory pointed to by `*lineptr`

As all functions from Dynamic Memory TS, `getline` is only guaranteed to be available if __STDC_ALLOC_LIB__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT2__ to the integer constant 1 before including `stdio.h`.

### [edit] Parameters

lineptr | - | pointer to a pointer to the initial buffer or to a null pointer
n | - | pointer to the size of the initial buffer
delimiter | - | the delimiter character
stream | - | valid input stream, opened by fopen

### [edit] Return value

The number of characters stored in the buffer, including the delimiter, but excluding the null terminator.

On error, returns -1 and sets feof or ferror on `stream`.

### [edit] Notes

These functions are identical to their POSIX versions except that it is allowed, but not required to set errno on error.

### [edit] Example

Run this code

    #define __STDC_WANT_LIB_EXT2__ 1
    #include <stdio.h>
    #include <stdlib.h>
    void get_y_or_n(void)
    {
        char *response = NULL;
        size_t len;
        printf("Continue? [y] n: ");
        if((getline(&response, &len, stdin) < 0) || (len && response[0] == 'n')) {
            free(response);
            exit(0);
        }
        free(response);
        return;
    }
    int main()
    {
        get_y_or_n();
    }

Output:

    Continue? [y] n:

### [edit] See also

fgets | gets a character string from a file stream (function) [edit]
getsgets_s (until C11)(since C11) | reads a character string from `stdin` (function) [edit]
fgetws (C95) | gets a wide string from a file stream (function) [edit]
malloc | allocates memory (function) [edit]

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