Linux 腳本收集

括號的使用說明

參考：Double parenthesis with and without dollar

• $(…) means execute the command in the parens and return its stdout.

$ echo "The current date is $(date)"
The current date is Mon Jul  6 14:27:59 PDT 2015

• (…) means run the commands listed in the parens in a subshell. Example:

$ a=1; (a=2; echo "inside: a=$a"); echo "outside: a=$a"
inside: a=2
outside: a=1

• $((…)) means perform arithmetic and return the result of the calculation. Example:

$ a=$((2+3)); echo "a=$a"
a=5

• ((…)) means perform arithmetic, possibly changing the values of shell variables, but don’t return its result. Example:

$ ((a=2+3)); echo "a=$a"
a=5

• ${…} means return the value of the shell variable named in the braces. Example:

$ echo ${SHELL}
/bin/bash

• {…} means execute the commands in the braces as a group. Example:

$ false || { echo "We failed"; exit 1; }
We failed

有用腳本收集

文件讀取

讀取文件目錄的所有文件，按行讀取每個文件，判斷行文字是否包含特定字符串；如果包含，通過特殊字符來split並輸出想要的值。

#!/bin/sh
for filename in /home/okchem/mysqlbackup/*.sql; do
    while IFS= read line
    do
        # display $line or do somthing with $line
        if [[ $line == *"/ocf/"* ]]; then
            SUBSTRING=$(echo $line| cut -d'`' -f 2) # 用'`'來拆分,輸出數組第二個
            echo $SUBSTRING
        fi
    done <"${filename}.sql"
done