if...elif...fi 語句是提前一個(gè)級別的控制語句,形式出幾個(gè)條件,允許 Shell 作出正確的決定。
if [ expression 1 ]
then
Statement(s) to be executed if expression 1 is true
elif [ expression 2 ]
then
Statement(s) to be executed if expression 2 is true
elif [ expression 3 ]
then
Statement(s) to be executed if expression 3 is true
else
Statement(s) to be executed if no expression is true
fi
這段代碼沒有什么特別的。這僅僅是一個(gè)系列,if 語句每一個(gè)語句else子句的一部分。下面語句是執(zhí)行的基礎(chǔ)上的真實(shí)情況,如果條件不為 ture,則執(zhí)行else塊。
#!/bin/sh
a=10
b=20
if [ $a == $b ]
then
echo "a is equal to b"
elif [ $a -gt $b ]
then
echo "a is greater than b"
elif [ $a -lt $b ]
then
echo "a is less than b"
else
echo "None of the condition met"
fi
這將產(chǎn)生以下結(jié)果:
a is less than b
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