sd_journal_stream_fd

systemd

sd_journal_stream_fd_with_namespace

Create log stream file descriptor to the journal

#include <systemd/sd-journal.h>

int

sd_journal_stream_fd

const char *

identifier

int

priority

int

level_prefix

int

sd_journal_stream_fd_with_namespace

const char *

name_space

const char *

identifier

int

priority

int

level_prefix

Description

sd_journal_stream_fd() may be used to create a log stream file descriptor. Log messages written to this file descriptor as simple newline-separated text strings are written to the journal. This file descriptor can be used internally by applications or be made standard output or standard error of other processes executed.

sd_journal_stream_fd() takes a short program identifier string as first argument, which will be written to the journal as SYSLOG_IDENTIFIER= field for each log entry (see systemd.journal-fields(7) for more information). The second argument shall be the default priority level for all messages. The priority level is one of LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG, as defined in syslog.h, see syslog(3) for details. The third argument is a boolean: if true kernel-style log level prefixes (such as SD_WARNING) are interpreted, see sd-daemon(3) for more information.

sd_journal_stream_fd_with_namespace() is similar to sd_journal_stream_fd(), but takes an additional name_space parameter that specifies which journal namespace to operate on. If specified as NULL the call is identical to sd_journal_stream_fd(). For details about journal namespaces, see systemd-journald.service(8).

It is recommended that applications log UTF-8 messages only with this API, but this is not enforced.

Each invocation of these functions allocates a new log stream file descriptor, that is not shared with prior or later invocations. The file descriptor is write-only (its reading direction is shut down), and O_NONBLOCK is turned off initially.

Return Value

The call returns a valid write-only file descriptor on success or a negative errno-style error code.

Signal safety

sd_journal_stream_fd() and sd_journal_stream_fd_with_namespace() are "async signal safe" in the meaning of signal-safety(7).

Notes

Examples

Creating a log stream suitable for fprintf(3):

History

sd_journal_stream_fd() was added in version 187.

sd_journal_stream_fd_with_namespace() was added in version 256.