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GETDELIM(3P) POSIX Programmer's Manual GETDELIM(3P)
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.
getdelim, getline — read a delimited record from stream
#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);
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().
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.
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:
EOVERFLOW
More than {SSIZE_MAX} characters were read without
encountering the delimiter character.
The following sections are informative.
#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;
}
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.
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.
None.
Section 2.5, Standard I/O Streams, fgetc(3p), fgets(3p), free(3p)
The Base Definitions volume of POSIX.1‐2008, stdio.h(0p)
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 .
IEEE/The Open Group 2013 GETDELIM(3P)
Pages that refer to this page: stdio.h(0p), fgets(3p), getline(3p)