getline() — Read an entire line from a stream

Standards

Format

#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
ssize_t getline(char **__restrict__ lineptr, size_t *__restrict__ n, FILE *__restrict__ stream);

General description

The getline() function reads an entire line from stream, storing the address of the buffer containing the text into *lineptr. The buffer is null-terminated and includes the newline character, if one is found.

If *lineptr is set to NULL and *n is set 0 before the call, getline() allocates a buffer for storing the line. This buffer must be freed by the user program even when getline() fails.

Alternatively, before calling getline(), *lineptr can contain a pointer to a buffer that is allocated by malloc(), which is *n bytes in size. If the buffer is not large enough to hold the line, getline() resizes it with realloc(), updating *lineptr and *n as necessary.

In either case, on a successful call, *lineptr and *n are updated to reflect the buffer address and allocated size respectively.

Returned value

If successful, getline() returns the number of characters that are read, including the newline character, but not including the terminating null byte (‘\0’). This value can be used to handle embedded null bytes in the line read.

Related information

• fopen() — Open a file
• fclose() — Close file