# sd_journal_stream_fd

## NAME



           sd_journal_stream_fd, sd_journal_stream_fd_with_namespace - Create
           log stream file descriptor to the journal
    


## SYNOPSIS



           **#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



           All functions listed here are thread-safe and may be called in
           parallel from multiple threads.
    
           Functions described here are available as a shared library, which
           can be compiled against and linked to with the
           **libsystemd pkg-config**(1) file.
    


## EXAMPLES



           Creating a log stream suitable for fprintf(3):
    
               /* SPDX-License-Identifier: MIT-0 */
    
               #define _GNU_SOURCE 1
               #include <errno.h>
               #include <syslog.h>
               #include <stdio.h>
               #include <unistd.h>
               #include <systemd/sd-journal.h>
               #include <systemd/sd-daemon.h>
    
               int main(int argc, char *argv[]) {
                 int fd;
                 FILE *log;
    
                 fd = sd_journal_stream_fd("test", LOG_INFO, 1);
                 if (fd < 0) {
                   fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
                   return 1;
                 }
    
                 log = fdopen(fd, "w");
                 if (!log) {
                   fprintf(stderr, "Failed to create file object: %s\n", strerror(errno));
                   close(fd);
                   return 1;
                 }
                 fprintf(log, "Hello World!\n");
                 fprintf(log, SD_WARNING "This is a warning!\n");
                 fclose(log);
                 return 0;
               }
    


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