man_3_getline.txt

GETLINE(3)                         Linux Programmer's Manual                        GETLINE(3)

NAME
       getline, getdelim - delimited string input

SYNOPSIS
       #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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       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 contain‐
       ing the text into *lineptr.  The buffer is null-terminated  and  includes  the  newline
       character, if one was found.

       If  *lineptr  is set to NULL and *n is set 0 before the call, then getline() will allo‐
       cate 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 mal‐
       loc(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 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.

       Both functions return -1 on failure to read a line (including  end-of-file  condition).
       In the event of an error, errno is set to indicate the cause.

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).

       ┌──────────────────────┬───────────────┬─────────┐
       │Interface             │ Attribute     │ Value   │
       ├──────────────────────┼───────────────┼─────────┤
       │getline(), getdelim() │ Thread safety │ MT-Safe │
       └──────────────────────┴───────────────┴─────────┘

CONFORMING TO
       Both  getline()  and getdelim() were originally GNU extensions.  They were standardized
       in POSIX.1-2008.

EXAMPLE
       #define _GNU_SOURCE
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           FILE *stream;
           char *line = NULL;
           size_t len = 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, &len, stream)) != -1) {
               printf("Retrieved line of length %zu:\n", nread);
               fwrite(line, nread, 1, stdout);
           }

           free(line);
           fclose(stream);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       read(2), fgets(3), fopen(3), fread(3), scanf(3)

COLOPHON
       This page is part of release 5.05 of the Linux man-pages project.  A description of the
       project,  information about reporting bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.

GNU                                       2019-03-06                                GETLINE(3)