Detailed introduction to basic learning of Linux shell scripts (7)-PHP Tutorial-php.cn

Detailed introduction to basic learning of Linux shell scripts (7)

黄舟

Release： 2023-03-05 11:48:02

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Linux shell脚本基础学习这部分如果只看前面间的理论部分虽然有一些例子，但是还不够系统，这里将以具体实例给大家展现Linux shell脚本编程，以帮助大家完善Linux shell基础的学习和提高。
第2部分实例
现在我们来讨论编写一个脚本的一般步骤。任何优秀的脚本都应该具有帮助和输入参数。并且写一个伪脚本（framework.sh），该脚本包含了大多数脚本都需要的框架结构，是一个非常不错的主意。这时候，在写一个新的脚本时我们只需要执行一下copy命令：

cp framework.sh myscript

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然后再插入自己的函数。
让我们再看个例子：
二进制到十进制的转换
脚本 b2d 将二进制数 (比如 1101) 转换为相应的十进制数。这也是一个用expr命令进行数学运算的例子：

#!/bin/sh
# vim: set sw=4 ts=4 et:
help()
{
cat <
b2h -- convert binary to decimal
USAGE: b2h [-h] binarynum
OPTIONS: -h help text
EXAMPLE: b2h 111010
will return 58
HELP
exit 0
}
error()
{
# print an error and exit
echo "$1"
exit 1
}
lastchar()
{
# return the last character of a string in $rval
if [ -z "$1" ]; then
# empty string
rval=""
return
fi
# wc puts some space behind the output this is why we need sed:
numofchar=`echo -n "$1" | wc -c | sed &#39;s/ //g&#39; `
# now cut out the last char
rval=`echo -n "$1" | cut -b $numofchar`
}
chop()
{
# remove the last character in string and return it in $rval
if [ -z "$1" ]; then
# empty string
rval=""
return
fi
# wc puts some space behind the output this is why we need sed:
numofchar=`echo -n "$1" | wc -c | sed &#39;s/ //g&#39; `
if [ "$numofchar" = "1" ]; then
# only one char in string
rval=""
return
fi
numofcharminus1=`expr $numofchar "-" 1`
# now cut all but the last char:
rval=`echo -n "$1" | cut -b 0-${numofcharminus1}`
}
while [ -n "$1" ]; do
case $1 in
-h) help;shift 1;; # function help is called
--) shift;break;; # end of options
-*) error "error: no such option $1. -h for help";;
*) break;;
esac
done
# The main program
sum=0
weight=1
# one arg must be given:
[ -z "$1" ] && help
binnum="$1"
binnumorig="$1"
while [ -n "$binnum" ]; do
lastchar "$binnum"
if [ "$rval" = "1" ]; then
sum=`expr "$weight" "+" "$sum"`
fi
# remove the last position in $binnum
chop "$binnum"
binnum="$rval"
weight=`expr "$weight" "*" 2`
done
echo "binary $binnumorig is decimal $sum"

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该脚本使用的算法是利用十进制和二进制数权值 (1,2,4,8,16,..)，比如二进制"10"可以这样转换成十进制：