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getdelim.3p (6251B)

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.TH GETDELIM "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH 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.
.\"
.SH NAME
getdelim, getline
\(em read a delimited record from
.IR stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>
.P
ssize_t getdelim(char **restrict \fIlineptr\fP, size_t *restrict \fIn\fP,
    int \fIdelimiter\fP, FILE *restrict \fIstream\fP);
ssize_t getline(char **restrict \fIlineptr\fP, size_t *restrict \fIn\fP,
    FILE *restrict \fIstream\fP);
.fi
.SH DESCRIPTION
The
\fIgetdelim\fR()
function shall read from
.IR stream
until it encounters a character matching the
.IR delimiter
character. The
.IR delimiter
argument is an
.BR int ,
the value of which the application shall ensure is a character
representable as an
.BR "unsigned char"
of equal value that terminates the read process. If the
.IR delimiter
argument has any other value, the behavior is undefined.
.P
The application shall ensure that
.IR *lineptr
is a valid argument that could be passed to the
\fIfree\fR()
function. If
.IR *n
is non-zero, the application shall ensure that
.IR *lineptr
either points to an object of size at least
.IR *n
bytes, or is a null pointer.
.P
If
.IR *lineptr
is a null pointer or if the object pointed to by
.IR *lineptr
is of insufficient size, an object shall be allocated as if by
\fImalloc\fR()
or the object shall be reallocated as if by
\fIrealloc\fR(),
respectively, such that the object is large enough to hold
the characters to be written to it, including the terminating NUL,
and
.IR *n
shall be set to the new size. If the object was allocated,
or if the reallocation operation moved the object,
.IR *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.
.P
The
\fIgetline\fR()
function shall be equivalent to the
\fIgetdelim\fR()
function with the
.IR delimiter
character equal to the
<newline>
character.
.P
The
\fIgetdelim\fR()
and
\fIgetline\fR()
functions may mark the last data access timestamp of the file associated
with
.IR stream
for update. The last data access timestamp shall be marked for update
by the first successful execution of
\fIfgetc\fR(),
\fIfgets\fR(),
\fIfread\fR(),
\fIfscanf\fR(),
\fIgetc\fR(),
\fIgetchar\fR(),
\fIgetdelim\fR(),
\fIgetline\fR(),
\fIgets\fR(),
or
\fIscanf\fR()
using
.IR stream
that returns data not supplied by a prior call to
\fIungetc\fR().
.SH "RETURN VALUE"
Upon successful completion, the
\fIgetline\fR()
and
\fIgetdelim\fR()
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
.IR errno
to indicate the error.
.SH ERRORS
For the conditions under which the
\fIgetdelim\fR()
and
\fIgetline\fR()
functions shall fail and may fail, refer to
.IR "\fIfgetc\fR\^(\|)".
.P
In addition, these functions shall fail if:
.TP
.BR EINVAL
.IR lineptr
or
.IR n
is a null pointer.
.TP
.BR ENOMEM
Insufficient memory is available.
.br
.P
These functions may fail if:
.TP
.BR EOVERFLOW
The number of bytes to be written into the buffer, including the
delimiter character (if encountered), would exceed
{SSIZE_MAX}.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
.sp
.RS 4
.nf
#include <stdio.h>
#include <stdlib.h>
.P
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 :\en", read);
        printf("%s", line);
    }
    if (ferror(fp)) {
        /* handle error */
    }
    free(line);
    fclose(fp);
    return 0;
}
.fi
.P
.RE
.SH "APPLICATION USAGE"
Setting
.IR *lineptr
to a null pointer and
.IR *n
to zero are allowed and a recommended way to start parsing a file.
.P
The
\fIferror\fR()
or
\fIfeof\fR()
functions should be used to distinguish between an error condition and
an end-of-file condition.
.P
Although a NUL terminator is always supplied after the line, note that
.IR strlen (* lineptr )
will be smaller than the return value if the line contains embedded
NUL characters.
.SH RATIONALE
These functions are widely used to solve the problem that the
\fIfgets\fR()
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.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.5" ", " "Standard I/O Streams",
.IR "\fIfgetc\fR\^(\|)",
.IR "\fIfgets\fR\^(\|)",
.IR "\fIfree\fR\^(\|)",
.IR "\fImalloc\fR\^(\|)",
.IR "\fIrealloc\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<stdio.h>\fP"
.\"
.SH 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 .
.PP
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 .