This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       Setting  *lineptr  to  a null pointer and *n to zero are allowed and a recommended way to start parsing a
       file.

       The ferror() or feof() functions should be used to distinguish between an error condition and an  end-of-
       file condition.

       Although  a  NUL terminator is always supplied after the line, note that strlen(*lineptr) will be smaller
       than the return value if the line contains embedded NUL characters.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee  document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                      GETDELIM(3POSIX)

       The  getdelim()  function  shall  read from stream until it encounters a character matching the delimiter
       character. The delimiter argument is an int, the value  of  which  the  application  shall  ensure  is  a
       character  representable  as  an  unsignedchar  of equal value that terminates the read process. If the
       delimiter argument has any other value, the behavior is undefined.

       The application shall ensure that *lineptr is a valid  argument  that  could  be  passed  to  the  free()
       function.  If  *n  is  non-zero, the application shall ensure that *lineptr either points to an object of
       size at least *n bytes, or is a null pointer.

       If *lineptr is a null pointer or if the object pointed to by *lineptr is of insufficient size, an  object
       shall be allocated as if by malloc() or the object shall be reallocated as if by realloc(), respectively,
       such  that  the  object  is  large  enough  to  hold  the  characters  to be written to it, including the
       terminating NUL, and *n shall be set to the new size. If the object was allocated, or if the reallocation
       operation moved the object, *lineptr shall be updated to point to the new object or  new  location.   The
       characters read, including any delimiter, shall be stored in the object, and a terminating NUL added when
       the delimiter or end-of-file is encountered.

       The  getline() function shall be equivalent to the getdelim() function with the delimiter character equal
       to the <newline> character.

       The getdelim() and getline() functions may mark the last data access timestamp  of  the  file  associated
       with stream for update. The last data access timestamp shall be marked for update by the first successful
       execution  of  fgetc(),  fgets(), fread(), fscanf(), getc(), getchar(), getdelim(), getline(), gets(), or
       scanf() using stream that returns data not supplied by a prior call to ungetc().

       For  the  conditions under which the getdelim() and getline() functions shall fail and may fail, refer to
       fgetc().

       In addition, these functions shall fail if:

       EINVALlineptr or n is a null pointer.

       ENOMEM Insufficient memory is available.

       These functions may fail if:

       EOVERFLOW
              The number of bytes to  be  written  into  the  buffer,  including  the  delimiter  character  (if
              encountered), would exceed {SSIZE_MAX}.

       Thefollowingsectionsareinformative.

           #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(1);
               while ((read = getline(&line, &len, fp)) != -1) {
                   printf("Retrieved line of length %zu :\n", read);
                   printf("%s", line);
               }
               if (ferror(fp)) {
                   /* handle error */
               }
               free(line);
               fclose(fp);
               return 0;
           }

       None.

       getdelim, getline — read a delimited record from stream

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       These functions are widely used to solve the problem that the fgets() function has with long  lines.  The
       functions  automatically  enlarge  the  target  buffers if needed. These are especially useful since they
       reduce code needed for applications.

       Upon successful completion, the getline() and getdelim() functions  shall  return  the  number  of  bytes
       written  into  the  buffer,  including  the  delimiter  character  if one was encountered before EOF, but
       excluding the terminating NUL character. If the end-of-file indicator for the stream is  set,  or  if  no
       characters  were read and the stream is at end-of-file, the end-of-file indicator for the stream shall be
       set and the function shall return -1.  If an error occurs, the error indicator for the  stream  shall  be
       set, and the function shall return -1 and set errno to indicate the error.

Section2.5, StandardI/OStreams, fgetc(), fgets(), free(), malloc(), realloc()

       The Base Definitions volume of POSIX.1‐2017, <stdio.h>

       #include <stdio.h>

       ssize_t getdelim(char **restrict lineptr, size_t *restrict n,
           int delimiter, FILE *restrict stream);
       ssize_t getline(char **restrict lineptr, size_t *restrict n,
           FILE *restrict stream);