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GETLINE (3) | C library functions | Unix Manual Pages | :man


getline, getdelim - delimited string input




#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);


getline() reads an entire line, storing the address of the buffer containing the text into "*lineptr". The buffer is null-terminated and includes the newline character, if a newline delimiter was found.

If "*lineptr" is "NULL", the getline() routine will allocate a buffer for containing the line, which must be freed by the user program. Alternatively, before calling "getline()", "*lineptr" can contain a pointer to a "malloc()"-allocated buffer "*n" bytes in size. If the buffer is not large enough to hold the line read in, getline() resizes the buffer to fit with "realloc()", 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 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.


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

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


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


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


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


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

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