Shell Script Learn

The previous writing test program used scripts to raise interest, combined with specific cases, to test the results of learning. Finally understand a slightly more complex shell script. There are still a lot of technical things in there.

Declared variable name, Bluetooth_sleep_path is not used for [HTML] view plain copy bluetooth_sleep_path=/proc/bluetooth/sleep/proto log_tag= " Qcom-bluetooth "Log_name=" ${0}: "

declaring functions

$#----The total number of arguments passed to the program
$?----the previous code or shell program exits in the shell, returns 0 if normal exits, and a non-0 value instead. The
$*----A string that consists of all the arguments passed to the program.
    $-----provide options when the shell starts or uses the SET command
    $?----The value returned after the previous command was executed
     $$----The current shell's process number
    $!----The process number of the previous child process
    $@----All parameters, each enclosed in double brackets
    $n----Positional parameter value, n for position
    $----Current shell name [html]  view Plain copy loge  () & nbsp;  {     /system/bin/log -t  $LOG _tag -p e  "$LOG _name  $@ "  }      logi  ()    {     /system/bin/log  -t  $LOG _tag -p i  "$LOG _name $@"   }      failed  ()    {     loge  "$1: exit code $2"      exit  $2  }  

& Symbols I understand the meaning of running in the background so that $! represents the process number of the previous subprocess, and the usage can refer to test2.sh [html]  view plain copy start_hciattach  ()     {     /system/bin/hciattach -n  $BTS _device  $BTS _type  $BTS _baud  &     hciattach_pid=$!     logi  "start_hciattach:  pid =  $hciattach _pid "     echo 1 >  $BLUETOOTH _sleep_path   }      kill_hciattach  ()    {     echo 0  >  $BLUETOOTH _sleep_path     logi  "kill_hciattach: pid = $ Hciattach_pid "     ## careful not to kill zero or null!      kill -TERM  $hciattach _pid     # this shell  DOESN ' t exit now -- wait returns for normal exit  }   

The

gets the parameters and resolves them, similar to the C language. BLNP is without parameters, t:s: With a colon for parameters,
Default output usage [html]  view plain copy while getopts  "blnpt:s:"  f    do     case  $f  in     b | l |  n | p)   opt_flags= "$opt _flags -$f"  ;;      t)       timeout= $OPTARG;;      s)       initial_speed= $OPTARG;;      \?)      echo  $USAGE; exit 1;;      esac   done   shift $ (($OPTIND-1))