---
name: "getline"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/getline"
---

# getline(3)

delimited string input

## NAME

getline, getdelim - delimited string input

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <stdio.h>
```

**ssize\_t getline(char \*\*restrict** *lineptr***, size\_t \*restrict** *n***,**                 **FILE \*restrict** *stream***);** **ssize\_t getdelim(char \*\*restrict** *lineptr***, size\_t \*restrict** *n***,**                 **int** *delim***, FILE \*restrict** *stream***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**getline**(), **getdelim**():

```
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _GNU_SOURCE
```

## DESCRIPTION

**getline**() 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 was found.

If *\*lineptr* is set to NULL before the call, then **getline**() will allocate a buffer for storing the line. This buffer should be freed by the user program even if **getline**() failed.

Alternatively, before calling **getline**(), *\*lineptr* can contain a pointer to a [**malloc**(3)](/malloc/3.md)-allocated buffer *\*n* bytes in size. If the buffer is not large enough to hold the line, **getline**() resizes it with [**realloc**(3)](/realloc/3.md), updating *\*lineptr* and *\*n* as necessary.

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

**getdelim**() works like **getline**(), except that a line delimiter other than newline can be specified as the *delimiter* argument. As with **getline**(), a delimiter character is not added if one was not present in the input before end of file was reached.

## RETURN VALUE

On success, **getline**() and **getdelim**() return the number of characters read, including the delimiter character, but not including the terminating null byte ('\\0'). This value can be used to handle embedded null bytes in the line read.

At end of file, both functions return -1 with the file stream end-of-file indicator set. On error, both functions return -1 with the file stream error indicator set, and *errno* is set to indicate the error.

If *\*lineptr* was set to NULL before the call, then the buffer should be freed by the user program even on failure.

## ERRORS

- **EINVAL**

  Bad arguments (*n* or *lineptr* is NULL, or *stream* is not valid).

- **ENOMEM**

  Allocation or reallocation of the line buffer failed.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **getline**(), **getdelim**() | Thread safety | MT-Safe |

## STANDARDS

POSIX.1-2008.

## HISTORY

GNU, POSIX.1-2008.

## EXAMPLES

```
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
    FILE *stream;
    char *line = NULL;
    size_t size = 0;
    ssize_t nread;
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <file>\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    stream = fopen(argv[1], "r");
    if (stream == NULL) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }
    while ((nread = getline(&line, &size, stream)) != -1) {
        printf("Retrieved line of length %zd:\n", nread);
        fwrite(line, nread, 1, stdout);
    }
    free(line);
    fclose(stream);
    exit(EXIT_SUCCESS);
}
```

## SEE ALSO

[**read**(2)](/read/2.md), [**fgets**(3)](/fgets/3.md), [**fopen**(3)](/fopen/3.md), [**fread**(3)](/fread/3.md), [**scanf**(3)](/scanf/3.md)