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  containing  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 allocate 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 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 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).

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(void)
   {
       FILE *stream;
       char *line = NULL;
       size_t len = 0;
       ssize_t read;

       stream = fopen("/etc/motd", "r");
       if (stream == NULL)
           exit(EXIT_FAILURE);

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

       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 4.09 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/.

---

Free and Open Source Software