'\" t
.TH "SD_DEVICE_ENUMERATOR_NEW" "3" "" "systemd 258.2" "sd_device_enumerator_new"
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.nh
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.SH "NAME"
sd_device_enumerator_new, sd_device_enumerator_ref, sd_device_enumerator_unref, sd_device_enumerator_unrefp \- Create, reference, and release a device enumerator object
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-device\&.h>
.fi
.ft
.HP \w'int\ sd_device_enumerator_new('u
.BI "int sd_device_enumerator_new(sd_device_enumerator\ **" "ret" ");"
.HP \w'sd_device_enumerator*\ sd_device_enumerator_ref('u
.BI "sd_device_enumerator* sd_device_enumerator_ref(sd_device_enumerator\ *" "enumerator" ");"
.HP \w'sd_device_enumerator*\ sd_device_enumerator_unref('u
.BI "sd_device_enumerator* sd_device_enumerator_unref(sd_device_enumerator\ *" "enumerator" ");"
.HP \w'void\ sd_device_enumerator_unrefp('u
.BI "void sd_device_enumerator_unrefp(sd_device_enumerator\ **" "enumerator" ");"
.SH "DESCRIPTION"
.PP
The
\fBsd_device_enumerator\fR
family of functions provides a way to iterate over devices recognized by
\fBsystemd-udevd\fR(8)\&. The enumerator allows filtering and matching devices by subsystem, properties and other attributes\&.
.PP
\fBsd_device_enumerator_new()\fR
creates a new device enumerator object and stores the result in the pointer referenced by
\fIret\fR\&. Returns 0 on success, or a negative errno\-style error code on failure\&.
.PP
\fBsd_device_enumerator_ref()\fR
increases the reference count of the specified
\fIenumerator\fR
by one\&.
.PP
\fBsd_device_enumerator_unref()\fR
decreases the reference count of the
\fIenumerator\fR
by one\&. When the reference count reaches zero, the enumerator object is destroyed and cannot be used anymore, so further calls to
\fBsd_device_enumerator_unref() \fR
or
\fBsd_device_enumerator_unrefp()\fR
are illegal\&.
.PP
\fBsd_device_enumerator_unrefp()\fR
is similar to
\fBsd_device_enumerator_unref()\fR
but takes a pointer to a pointer to an
\fBsd_device_enumerator\fR
object\&. This call is useful in conjunction with GCC\*(Aqs and LLVM\*(Aqs
\m[blue]\fBClean\-up Variable Attribute\fR\m[]\&\s-2\u[1]\d\s+2\&. Note that this function is defined as an inline function\&. Use a declaration like the following, in order to allocate a
\fBsd_device_enumerator\fR
object that is freed automatically as the code block is left:
.sp
.if n \{\
.RS 4
.\}
.nf
{
  __attribute__((cleanup(sd_device_enumerator_unrefp))) sd_device_enumerator *enumerator = NULL;
  int r;
  \&...
  r = sd_device_enumerator_new(&enumerator);
  if (r < 0)
    fprintf(stderr, "Failed to allocate sd_device_enumerator: %s\en", strerror(\-r));
  \&...
}
.fi
.if n \{\
.RE
.\}
.PP
\fBsd_device_enumerator_ref()\fR
and
\fBsd_device_enumerator_unref()\fR
execute no operation if the
\fIenumerator\fR
is
\fBNULL\fR\&.
\fBsd_device_enumerator_unrefp()\fR
will first dereference its argument, which must not be
\fBNULL\fR, and will execute no operation if
\fIthat\fR
is
\fBNULL\fR\&.
.SH "RETURN VALUE"
.PP
\fBsd_device_enumerator_new()\fR
returns 0 on success or a negative errno\-style error code on failure\&.
.PP
\fBsd_device_enumerator_ref()\fR
always returns the enumerator pointer\&.
.PP
\fBsd_device_enumerator_unref()\fR
always returns
\fBNULL\fR\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-ENOMEM\fR
.RS 4
Memory allocation failed\&.
.RE
.PP
\fB\-EINVAL\fR
.RS 4
The argument is invalid\&.
.RE
.SH "EXAMPLE"
.PP
\fBExample\ \&1.\ \&Using sd_device_enumerator_new()\fR
.sp
.if n \{\
.RS 4
.\}
.nf
/* SPDX\-License\-Identifier: MIT\-0 */

#include <stdio\&.h>
#include <systemd/sd\-device\&.h>

int main(void) {
    sd_device_enumerator *enumerator;
    int r;

    r = sd_device_enumerator_new(&enumerator);
    if (r < 0) {
        fprintf(stderr, "Failed to create enumerator: %s\en", strerror(\-r));
        return 1;
    }

    sd_device_enumerator_ref(enumerator);
    sd_device_enumerator_unref(enumerator);

    sd_device_enumerator_unref(enumerator);

    return 0;
}
.fi
.if n \{\
.RE
.\}
.SH "HISTORY"
.PP
\fBsd_device_enumerator_new()\fR,
\fBsd_device_enumerator_ref()\fR,
\fBsd_device_enumerator_unref()\fR, and
\fBsd_device_enumerator_unrefp()\fR
were added in version 240\&.
.SH "SEE ALSO"
.PP
\fBsd_device_ref\fR(3), \fBsd_device_enumerator_add_match_parent\fR(3)
.SH "NOTES"
.IP " 1." 4
Clean-up Variable Attribute
.RS 4
\%https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
.RE