Shell condition judgment

Shell condition judgment
1. if condition judgment: if [condition]; then do something fi multiple conditions: & represents AND | represents OR multiple judgments: if [condition]; then do something elif [condition 2]; then // do something else // do someshing fi

#!/bin/bashread -p "Please input (Y/N) : " ynif [ "$yn" == "Y" ] || [ "$yn" == "y" ]; then     echo "Yes!"elif [ "$yn" == "N" ] || [ "$yn" == "n" ]; then     echo "No!"else    echo "Input Error"fiexit 0

View running results

[work@www sh]$ sh hello.sh Please input (Y/N) : yYes![work@www sh]$ sh hello.sh Please input (Y/N) : lInput Error[work@www sh]$

2. case judgment if there are many judgment levels in if, it is recommended to use case, otherwise there are too many nesting, and the code is prone to deterioration. Case $ variable name in "variable 1") do something; each end uses two semicolons (variable 2) do something ;;*) the last * indicates other values do something; esac:

#!/bin/bashcase $1 in    "one")        echo "One"        ;;    "two")        echo "Two"        ;;    *)        echo "Usage $0 (one|two)"        ;;esacexit 0

Running result

[work@ww sh]$ sh hello.sh Usage hello.sh (one|two)[work@www sh]$ sh hello.sh oneOne[work@www sh]$

Address: http://blog.csdn.net/yonggang7/article/details/40480695