getline(3) -- Linux man page



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).



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)
        return EXIT_SUCCESS;


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)