Shell 流程控制学习笔记

Shell 流程控制学习笔记
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if
for
while
until
case
select
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break#跳出所有循环
continue#仅仅跳出当前循环
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1、if
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if [ '1' == '1' ]
then
    echo '1'
else
    echo '2'
fi
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if [ '1' == '1' ]; then echo '1'; else echo '2'; fi
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2、for
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for i in 1 2 3
do
    echo $i
done
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for i in 1 2 3; do echo $i; done
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3、while
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while condition
do
    command
done
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while :
#无限循环写法注意是冒号
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3、until
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until condition
do
    command
done
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3、case
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case $1 in
  1)
    echo '1';;
  2)
    echo '2';;
  *)
    echo '555';;
esac
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case $1 in 1) echo '1';; 2) echo '2';; *) echo '555';; esac
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3、select
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PS3='12:'
#Shell脚本中使用select时的提示符
select i in '1' '2'
do
    echo '$1'
    break
done
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PS3='123';select i in '1' '2'; do echo '$1';break; done
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