GETDELIM(3)                POSIX Programmer's Manual               GETDELIM(3)



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

NAME
       getdelim, getline -- read a delimited record from stream

SYNOPSIS
       #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);

DESCRIPTION
       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 unsigned char 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().

RETURN VALUE
       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.

ERRORS
       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:

       EINVAL lineptr 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}.

       The following sections are informative.

EXAMPLES
           #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;
           }

APPLICATION USAGE
       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.

RATIONALE
       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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Section 2.5, Standard I/O Streams, fgetc(), fgets(), free(), malloc(),
       realloc()

       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 .



IEEE/The Open Group                  2017                          GETDELIM(3)
