GETDELIM(3P)

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
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.

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

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()

The Base Definitions volume of POSIX.1-2008, <stdio.h>

COPYRIGHT
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 http://www.unix.org/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 .