bash 使用 sed 在 txt 文件的第 1 行插入一个变量
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Insert a variable at line #1 of txt file using sed
提问by MLSC
I have the following bash:
我有以下 bash：
#!/bin/bash
if ["$#" -ne "1"]; then
echo "Usage: `basename $IPADDR
` <HOSTNAME>"
exit 1
fi
IPADDR=`ifconfig | head -2 | tail -1 | cut -d: -f2 | rev | cut -c8-23 | rev`
sed -i -e '1i$IPADDR \' /etc/hosts
But when I cat /etc/hosts:
但是当我cat /etc/hosts：
sed -i -e '1i'$IPADDR' ''\' /etc/hosts
How can I deal with such issues?
我该如何处理此类问题？
回答by Benjamin Bannier
Your problem is that variables inside single quotes 'aren't expanded by the shell, but left unchanged. To quote variables you want expanded use double quotes "or just leave off the quotes if they are unneeded like here, e.g.
您的问题是单引号内的变量'没有被 shell 扩展，而是保持不变。要引用您想要扩展的变量，请使用双引号，"或者如果不需要像这里这样的引号，则省略引号，例如
#!/bin/bash
IPADDR=$(/sbin/ifconfig | head -2 | tail -1 | cut -d: -f2 | rev | cut -c8-23 | rev)
sed -i -e "1i${IPADDR} " /etc/hosts
In above line $IPADDRand $1are outside of quotes and will be expanded by the shell before the arguments are being feed to sed.
在上面的行中$IPADDR，$1并且在引号之外，并且在将参数提供给sed.
回答by chooban
The single quotes mean the string isn't interpolated as a variable.
单引号表示该字符串未作为变量进行插值。
##代码##I also did the command in $(...)out of habit!
我也$(...)习惯性地做了命令！
