PROLOG

       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.

NAME

       fgets — get a string from a stream

SYNOPSIS

       #include <stdio.h>

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

DESCRIPTION

       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().

RETURN VALUE

       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.

ERRORS

       Refer to fgetc().

       The following sections are informative.

EXAMPLES

   Reading Input
       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);
           ...

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.5, Standard I/O Streams, fgetc(), fopen(), fread(), fscanf(), getc(), getchar(),
       getdelim(), gets(), ungetc()

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

COPYRIGHT

       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 .