Identifier interpretation

The following table provides a comprehensive understanding of various identifiers used in the system. These identifiers are replaced with specific values before the parsing process to write generic frontend files. If an identifier is invalid, it will remain unchanged. In this context, the term user refers to the owner of the process.

Identifier	Meaning	Replaced by
@I	Instance name	For instantiated services, this is the string between the first @ character and the rest of the instantiated service name. For non-instantiated services, it is the service name.
@U	User name	The user name. If the user is 0, it is replaced by root.
@u	User UID	The numeric user ID (UID).
@G	User group	The user group name.
@g	User GID	The numeric group ID (GID).
@H	User home directory	The user's home directory. For user 0, it is /root.
@S	User shell	The user’s shell.
@R	User runtime directory	The user's runtime directory. For user 0, it is /run; for other users, it corresponds to $XDG_RUNTIME_DIR.

By understanding these identifiers and their replacements, you can effectively create and manage service files, ensuring that user-specific details are correctly populated during the service parsing process.

Examples of identifiers usage

• Using @R identifier

  Original file: dbus@

  [Main]
  Type = classic
  Version = 0.7.0
  Description = "dbus session daemon for @U user"
  User = ( user )
  MaxDeath = 3
  Notify = 4
  TimeoutStart = 3000
  
  [Start]
  Execute = (
      /usr/bin/execl-cmdline -s { /usr/bin/dbus-daemon ${Args} }
  )
  
  [Stop]
  Execute = (
      /usr/bin/s6-rmrf ${Socket}
  )
  
  [Environment]
  Args=!--session --print-pid=4 --nofork --nopidfile --address=unix:path=${Socket}
  Socket=!@R/bus
  

  Result after calling 66 parse dbus@oblive where oblive has UID 1000

  [Main]
  Type = classic
  Version = 0.7.0
  Description = "dbus session daemon for oblive user"
  User = ( user )
  MaxDeath = 3
  Notify = 4
  TimeoutStart = 3000
  
  [Start]
  Execute = (
      /usr/bin/execl-cmdline -s { /usr/bin/dbus-daemon ${Args} }
  )
  
  [Stop]
  Execute = (
      /usr/bin/s6-rmrf ${Socket}
  )
  
  [Environment]
  Args=!--session --print-pid=4 --nofork --nopidfile --address=unix:path=${Socket}
  Socket=!/run/user/1000/bus
  

  In this example, the @R identifier is replaced by /run/user/1000, updating the Socket field with the correct runtime directory for the user oblive. The @U identifier is replaced by oblive in the Description field.

• Using @I identifier

  Original file: tty@

  [Main]
  Type = classic
  Version = 0.0.1
  Description = "Launch @I"
  User = ( root )
  
  [Start]
  Execute = ( agetty -J 38400 @I )
  

  Result after calling 66 parse tty@tty1

  [Main]
  Type = classic
  Version = 0.0.1
  Description = "Launch tty1"
  User = ( root )
  
  [Start]
  Execute = ( agetty -J 38400 tty1 )
  

  In this example, the @I identifier is replaced by tty1, resulting in the Description and Execute fields being updated accordingly.