Android init language与init.rc初始化脚本

service <name> <pathname> [ <argument> ]*
   <option>
   <option>

service logd /system/bin/logd
     class core
     socket logd stream 0666 logd logd
     socket logdr seqpacket 0666 logd logd
     socket logdw dgram 0222 logd logd
     group root system
      writepid /dev/cpuset/system-background/tasks
 service healthd /sbin/healthd
    class core
    critical
    seclabel u:r:healthd:s0
# Actions
# on <trigger>      
on property:sys.powerctl=*
    powerctl ${sys.powerctl}
on early-init
    # Set init and its forked children's oom_adj.
    write /proc/1/oom_score_adj -1000
    # Set the security context of /adb_keys if present.
    restorecon /adb_keys
    start ueventd

import /init.environ.rc
import /init.usb.rc
import /init.${ro.hardware}.rc
import /init.usb.configfs.rc
import /init.${ro.zygote}.rc
import /init.trace.rc

on early-init
     <command>
 on init
     <command>
 on late-init
     <command>
on post-fs
   <command>
on boot
   <command>
on property:sys.init_log_level=*  //在设置属性值时触发
   <command>
on charger
   <command>
on property:sys.powerctl=*
   <command>

bootchart_init
     Start bootcharting if configured (see below).
     This is included in the default init.rc.
  chmod <octal-mode> <path>
     Change file access permissions.
  chown <owner> <group> <path>
     Change file owner and group.
 class_start <serviceclass>
    Start all services of the specified class if they are
    not already running.
 class_stop <serviceclass>
    Stop and disable all services of the specified class if they are
    currently running.
 class_reset <serviceclass>
    Stop all services of the specified class if they are
    currently running, without disabling them. They can be restarted
    later using class_start.
 copy <src> <dst>
    Copies a file. Similar to write, but useful for binary/large
    amounts of data.
 domainname <name>
    Set the domain name.
 enable <servicename>
    Turns a disabled service into an enabled one as if the service did not
    specify disabled.
    If the service is supposed to be running, it will be started now.
    Typically used when the bootloader sets a variable that indicates a specific
    service should be started when needed. E.g.
      on property:ro.boot.myfancyhardware=1
         enable my_fancy_service_for_my_fancy_hardware
 exec [ <seclabel> [ <user> [ <group> ]* ] ] -- <command> [ <argument> ]*
    Fork and execute command with the given arguments. The command starts
    after "--" so that an optional security context, user, and supplementary
    groups can be provided. No other commands will be run until this one
    finishes. <seclabel> can be a - to denote default.
 export <name> <value>
    Set the environment variable <name> equal to <value> in the
    global environment (which will be inherited by all processes
    started after this command is executed)
 hostname <name>
    Set the host name.
 ifup <interface>
   Bring the network interface <interface> online.
 import <filename>
    Parse an init config file, extending the current configuration.
 insmod <path>
    Install the module at <path>
 load_all_props
    Loads properties from /system, /vendor, et cetera.
    This is included in the default init.rc.
 load_persist_props
    Loads persistent properties when /data has been decrypted.
    This is included in the default init.rc.
 loglevel <level>
    Sets the kernel log level to level. Properties are expanded within <level>.
 mkdir <path> [mode] [owner] [group]
    Create a directory at <path>, optionally with the given mode, owner, and
    group. If not provided, the directory is created with permissions 755 and
    owned by the root user and root group. If provided, the mode, owner and group
    will be updated if the directory exists already.
 mount_all <fstab>
    Calls fs_mgr_mount_all on the given fs_mgr-format fstab.
 mount <type> <device> <dir> [ <flag> ]* [<options>]
    Attempt to mount the named device at the directory <dir>
    <device> may be of the form mtd@name to specify a mtd block
    device by name.
    <flag>s include "ro", "rw", "remount", "noatime", ...
    <options> include "barrier=1", "noauto_da_alloc", "discard", ... as
    a comma separated string, eg: barrier=1,noauto_da_alloc
 powerctl
    Internal implementation detail used to respond to changes to the
    "sys.powerctl" system property, used to implement rebooting.
 restart <service>
    Like stop, but doesn't disable the service.
 restorecon <path> [ <path> ]*
    Restore the file named by <path> to the security context specified
   in the file_contexts configuration.
   Not required for directories created by the init.rc as these are
   automatically labeled correctly by init.
restorecon_recursive <path> [ <path> ]*
   Recursively restore the directory tree named by <path> to the
   security contexts specified in the file_contexts configuration.
rm <path>
   Calls unlink(2) on the given path. You might want to
   use "exec -- rm ..." instead (provided the system partition is
   already mounted).
rmdir <path>
   Calls rmdir(2) on the given path.
setprop <name> <value>
   Set system property <name> to <value>. Properties are expanded
   within <value>.
etrlimit <resource> <cur> <max>
   Set the rlimit for a resource.
start <service>
   Start a service running if it is not already running.
stop <service>
   Stop a service from running if it is currently running.
swapon_all <fstab>
   Calls fs_mgr_swapon_all on the given fstab file.
symlink <target> <path>
   Create a symbolic link at <path> with the value <target>
sysclktz <mins_west_of_gmt>
   Set the system clock base (0 if system clock ticks in GMT)
trigger <event>
   Trigger an event.  Used to queue an action from another
   action.
verity_load_state
  Internal implementation detail used to load dm-verity state.
verity_update_state <mount_point>
   Internal implementation detail used to update dm-verity state and
   set the partition.<mount_point>.verified properties used by adb remount
   because fs_mgr can't set them directly itself.
wait <path> [ <timeout> ]
   Poll for the existence of the given file and return when found,
   or the timeout has been reached. If timeout is not specified it
   currently defaults to five seconds.
write <path> <content>
   Open the file at <path> and write a string to it with write(2).
   If the file does not exist, it will be created. If it does exist,
   it will be truncated. Properties are expanded within <content>.

critical
   This is a device-critical service. If it exits more than four times in
   four minutes, the device will reboot into recovery mode.
 disabled
   This service will not automatically start with its class.
   It must be explicitly started by name.
 setenv <name> <value>
  Set the environment variable <name> to <value> in the launched process.
socket <name> <type> <perm> [ <user> [ <group> [ <seclabel> ] ] ]
  Create a unix domain socket named /dev/socket/<name> and pass
  its fd to the launched process.  <type> must be "dgram", "stream" or "seqpacket".
  User and group default to 0.
  'seclabel' is the SELinux security context for the socket.
  It defaults to the service security context, as specified by seclabel or
  computed based on the service executable file security context.
user <username>
  Change to username before exec'ing this service.
  Currently defaults to root.  (??? probably should default to nobody)
  Currently, if your process requires linux capabilities then you cannot use
  this command. You must instead request the capabilities in-process while
  still root, and then drop to your desired uid.
group <groupname> [ <groupname> ]*
  Change to groupname before exec'ing this service.  Additional
  groupnames beyond the (required) first one are used to set the
  supplemental groups of the process (via setgroups()).
  Currently defaults to root.  (??? probably should default to nobody)
seclabel <seclabel>
  Change to 'seclabel' before exec'ing this service.
 Primarily for use by services run from the rootfs, e.g. ueventd, adbd.
  Services on the system partition can instead use policy-defined transitions
  based on their file security context.
  If not specified and no transition is defined in policy, defaults to the init context.
oneshot
  Do not restart the service when it exits.
class <name>
  Specify a class name for the service.  All services in a
 named class may be started or stopped together.  A service
  is in the class "default" if one is not specified via the
 class option.
onrestart
  Execute a Command (see below) when service restarts.
writepid <file...>
  Write the child's pid to the given files when it forks. Meant for
  cgroup/cpuset usage.

service console /system/bin/sh
     class core
     console
     disabled
 #    user shell
 #    group shell log
 #    seclabel u:r:shell:s0

service start_mytest /system/bin/mytest.sh    
    oneshot
    on property:sys.boot_completed=1
    start start_mytest

#!/system/bin/sh
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0
echo "mytest ...!" > /dev/ttyS0