Shell_df

Disk Free (a.k.a ) disk availability

• Bash

  $ df
     
     Filesystem    512-blocks      Used Available Capacity iused      ifree %iused  Mounted on
     /dev/disk1s5   489825072  21732480  31137552    42%  487329 2448638031    0%   /
     devfs                382       382         0   100%     669          0  100%   /dev
     /dev/disk1s1   489825072 432330920  31137552    94% 1436221 2447689139    0%   /System/Volumes/Data
     /dev/disk1s4   489825072   2099304  31137552     7%       2 2449125358    0%   /private/var/vm
     map auto_home          0         0         0   100%       0          0  100%   /System/Volumes/Data/home
     
     
     
     
     
  $ df -h | awk '{print $1,$5}' 
  
  Filesystem Capacity
  /dev/disk1s5 42%
  devfs 100%
  /dev/disk1s1 94%
  /dev/disk1s4 7%
  map 0Bi
  

• Friendly＿Read Scripts

  #!bin/bash
  #another_df
  
  awkscript="/tmp/520a.sh" 
  
  trap "rm -f $awkscript" EXIT #(a.0) #(a.1)
  
  cat 'EOF' > $awkscript
  
  function showUnit(size){
  
   mb= size / 1024; okmb=(int(mb * 100)) / 100;
   gb= mb / 1024; okgb=(int(gb * 100)) / 100;
  
   if ( substr(size, 1, 1) !~ "[0~9]" || substr(size, 2, 1) !~"[0~9]" ){ return size } # (b.0) # (b.1) # (b.2)
   elif ( mb < 1 ){ return size "K"}
   elif  ( gb < 1 ){return okmb "M"}
   else { return okgb "G"}
  
  }
  
  Begin{
  
     printf "%-37s %10s %7s %7s %8s %-s\n", "FS", "Capacity", "Used", "Avail", "Ratio", "Mount_on" 
     #(c)
  
  }
  
  !/Filesystem/ {
  
    size=showUnit($2);
    used=showUnit($3);
    avail=showUnit($4);
  
    printf "", $1, size, used, avail, $5, $6
  }
  EOF
  
  df -k | awk -f $awkscript (d)
  
  exit 0
  

• Syntax

  • (a.0) trap

    將事件綁定到腳本的執行環境，參數1 是要執行的指令，參數2 是特定信號 signal 或是 事件 event。如本案例信號是 EXIT。

    這個 Trap 指令的優勢是無論在何時何處退出腳本，（即使不在腳本底部），它都能因為正確訊號或是間的聆聽，而在正確時間點出場，接手！

    假若有人是使用 ctrl-C 臨時退出程序，則此事件為 EXITQUIT (not 正常退出 SIGEXIT)。

  • (a.1) rm -f

  • (b.0) substr(size, start, length)

    https://www.wibibi.com/info.php?tid=96 (擷取字串方法)

  • (b.1)!~

  • (b.2) "[0~9]"

    https://github.com/QueenieCplusplus/Shell_echo/blob/master/README.md#0-9

  • (c) printf "%-37s"

    % means format
    -37 is a formats definition
    s means string
    

    https://blog.xuite.net/evan_0412/wretch/169912531-printf%28+%29的使用

  • (d) df -k | awk -f

• Execute Script

  $ df