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

       None.

       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                                         FGETS(3POSIX)

       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2017 defers to the ISO C standard.

       The  fgets()  function  shall  read  bytes from stream into the array pointed to by s until n-1 bytes are
       read, or a <newline> is read and transferred to s, or an end-of-file condition  is  encountered.  A  null
       byte  shall be written immediately after the last byte read into the array.  If the end-of-file condition
       is encountered before any bytes are read, the contents of the array pointed to by s shall not be changed.

       The fgets() function 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().

       Refer to fgetc().

       Thefollowingsectionsareinformative.

ReadingInput
       The  following  example  uses fgets() to read lines of input. It assumes that the file it is reading is a
       text file and that lines in this text file are no longer than 16384 (or {LINE_MAX} if  it  is  less  than
       16384  on  the  implementation where it is running) bytes long. (Note that the standard utilities have no
       line length limit if sysconf(_SC_LINE_MAX) returns -1 without setting errno.  This example  assumes  that
       sysconf(_SC_LINE_MAX) will not fail.)

           #include <limits.h>
           #include <stdio.h>
           #include <unistd.h>
           #define MYLIMIT 16384

           char *line;
           int line_max;
           if (LINE_MAX >= MYLIMIT) {
               // Use maximum line size of MYLIMIT. If LINE_MAX is
               // bigger than our limit, sysconf() cannot report a
               // smaller limit.
               line_max = MYLIMIT;
           } else {
               long limit = sysconf(_SC_LINE_MAX);
               line_max = (limit < 0 || limit > MYLIMIT) ? MYLIMIT : (int)limit;
           }

           // line_max + 1 leaves room for the null byte added by fgets().
           line = malloc(line_max + 1);
           if (line == NULL) {
               // out of space
               ...
               return error;
           }

           while (fgets(line, line_max + 1, fp) != NULL) {
               // Verify that a full line has been read ...
               // If not, report an error or prepare to treat the
               // next time through the loop as a read of a
               // continuation of the current line.
               ...
               // Process line ...
               ...
           }
           free(line);
           ...

       None.

       fgets — get a string from a 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.

       None.

       Upon  successful  completion,  fgets()  shall return s.  If the stream is at end-of-file, the end-of-file
       indicator for the stream shall be set and fgets() shall return a null pointer.  If a read  error  occurs,
       the error indicator for the stream shall be set, fgets() shall return a null pointer, and shall set errno
       to indicate the error.

Section2.5,  StandardI/OStreams, fgetc(), fopen(), fread(), fscanf(), getc(), getchar(), getdelim(),
       gets(), ungetc()

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

       #include <stdio.h>

       char *fgets(char *restrict s, int n, FILE *restrict stream);