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getline.3

GETLINE

Section: Linux Programmer's Manual (3)
Updated: 2006-05-17
Index Return to Main Contents
 

NAME

getline, getdelim - delimited string input  

SYNOPSIS

#define _GNU_SOURCE
#include <stdio.h>

ssize_t getline(char **lineptr, size_t *n, FILE *stream);

ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream);
 

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 NULL, then getline() will allocate a buffer for storing the line, which should be freed by the user program. (The value in *n is ignored.)

Alternatively, before calling getline(), *lineptr can contain a pointer to a malloc(3)-allocated buffer *n bytes in size. If the buffer is not large enough to hold the line, getline() resizes it with realloc(3), 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 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. This value can be used to handle embedded null bytes in the line read.

Both functions return -1 on failure to read a line (including end of file condition).  

ERRORS

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

CONFORMING TO

Both getline() and getdelim() are GNU extensions. They are available since libc 4.6.27.  

EXAMPLE

#define _GNU_SOURCE
#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(EXIT_FAILURE);

    while ((read = getline(&line, &len, fp)) != -1) {
        printf("Retrieved line of length %zu :\n", read);
        printf("%s", line);
    }

    if (line)
        free(line);
    exit(EXIT_SUCCESS);
}
 

SEE ALSO

read(2), fgets(3), fopen(3), fread(3), gets(3), scanf(3), feature_test_macros(7)  

COLOPHON

This page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
EXAMPLE
SEE ALSO
COLOPHON

 

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