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 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.


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).


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


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


#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); }


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


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