getdelim(3p) — Linux manual page


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

PROLOG         top

       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         top

       getdelim, getline — read a delimited record from stream

SYNOPSIS         top

       #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         top

       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.

       The size of the object pointed to by *lineptr shall be increased to
       fit the incoming line, if it isn't already large enough, including
       room for the delimiter and a terminating NUL. The characters read,
       including any delimiter, shall be stored in the string pointed to by
       the lineptr argument, 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         top

       Upon successful completion, the getline() and getdelim() functions
       shall return the number of characters written into the buffer,
       including the delimiter character if one was encountered before EOF,
       but excluding the terminating NUL character. If no characters were
       read, and the end-of-file indicator for the stream is set, or if 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         top

       For the conditions under which the getdelim() and getline() functions
       shall fail and may fail, refer to fgetc(3p).

       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:

              More than {SSIZE_MAX} characters were read without
              encountering the delimiter character.

       The following sections are informative.

EXAMPLES         top

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


       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         top

       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.



SEE ALSO         top

       Section 2.5, Standard I/O Streams, fgetc(3p), fgets(3p), free(3p)

       The Base Definitions volume of POSIX.1‐2008, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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 .

       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 .

IEEE/The Open Group                 2013                        GETDELIM(3P)

Pages that refer to this page: stdio.h(0p)fgets(3p)getline(3p)