Awk

Awk

‘{print}’ 指令

    awk '{print}' fileName

‘$0’,’$1’~’$N’ (N 為欄位數) $0: 一整行

example:

    ls -l | awk '{print $3,$9}'

    # linxinqi Applications
    # linxinqi Desktop
    # linxinqi Documents
    # linxinqi Downloads

, => 空格

    ls -l | awk '{print $3 $9}'

    # linxinqiApplications
    # linxinqiDesktop
    # linxinqiDocuments
    # linxinqiDownloads
    # linxinqiLibrary

自訂格式化輸出, 也可做數學運算

    # awk '{print $1 "\t" $3}' => 可輸出特殊格式字元
    ll | awk '{print "userName: ", $3, "fileName: ", $9}'

    # userName:  linxinqi fileName:  Applications
    # userName:  linxinqi fileName:  Desktop
    # userName:  linxinqi fileName:  Documents
    # userName:  linxinqi fileName:  Downloads

    awk '{print $1 + $2}' -    #  '-' 叫鍵盤出來
    # 1 2
    # 3

使用外部 script

    ls -l | awk -f {sciptFileName}

＝＝＝＝＝ advanced ＝＝＝＝＝

awk ‘BEGIN{statement} {main statement} END{statement}’
BEGIN, END 執行一次 main 可多次

String ~ /regex/[actions] => String match regex, then execute actions String !~ /regex/[actions] => String not match regex, then execute actions /regex/[actions] file => file match regex, then execute actions !/regex/[actions] file => file not match regex, then execute actions

“NF” => Number of Fields 印有幾段

    awk '{print NF}'  xxx.txt  

“NR” => Number of Records 可用來判斷條件

若是第七行, 則整行印出來

    awk 'NR == 7{print NR, $0}'

“ARGC” => number of arguments awk 'BEGIN {print "Arguments =", ARGC}' One Two Three Four => Arguments = 5

“ARGV” => input arguments in vector

    awk 'BEGIN { 
    for (i = 0; i < ARGC - 1; ++i) { 
        printf "ARGV[%d] = %s\n", i, ARGV[i] 
    } 
    }' one two three four

正則 /regularExpress/ 前綴符合 /^abc/ 後綴符合 /abc$/ 跳脫 //abc/ 跟java 一樣 /a[a-z]{3}c/ ^否定pattern /a[^a-z]c/ => abc -> 不合, aBc -> 符合

• => 可出現次數 0 ~ 無限 /a*b/

• => 可出現次數 1 ~ 無限 /a+b/ ? => 可有可沒有 /a?b/

    awk '/abc/{print $0}' data.txt

“FNR” => record number in current file “IGNORECASE” => ignore case “OFMT” => output format for numbers “RSTART” => index of first character matched by match “RLENGTH” => match length of string matched by match

reference: awk basic awk tutorial