Linux Bash Sed 一个班轮更改配置值 - 有空格或没有空格

Question

I need a Sed one liner to change a key = value pair in a config file, respecting the space or even no space between key and =

// config_file could look like this
key = oldValue
key=oldValue
key= oldValue
key =oldValue
keyABC = doNotMatchThis

What I got so far is this

sed -i '/key/s/= .*/= newValue/' config_file

The result will be

key = newValue
key=oldValue
key= newValue
key =oldValue
keyABC = newValue

keyABC changed also (very bad!). How can I achieve this?

What I want is

key = newValue
key=newValue
key= newValue
key =newValue
keyABC = doNotMatchThis

Answer 1

You may use

sed -i '/^key *=/s/=.*/= newValue/' config_file

The line qualitifier pattern is ^key *= :

• ^ - start of string
• key - a key string
• *= - 0 or more spaces and then = .

The substitution command is s/=.*/= newValue/ : it finds = and any 0+ chars after, and replaces with = newValue .

See the online sed demo .

s="key = oldValue
key=oldValue
key= oldValue
key =oldValue
keyABC = doNotMatchThis"

sed '/^key *=/s/=.*/= newValue/' <<< "$s"

Output:

key = newValue
key= newValue
key= newValue
key = newValue
keyABC = doNotMatchThis

Answer 2

With GNU sed.

sed -i -r 's/^(key *= *).*/\1newValue/' file

Output:

key = newValue
key=newValue
key= newValue
key =newValue
keyABC = doNotMatchThis

Answer 3

sed -i 's/\(key[[:space:]]\{0,1\}=[[:space:]]\{0,1\}\).*/\1 newValue/g' file

In case you want to match both tabs and spaces, use this instead:

sed -i 's/\(key[[:blank:]]\{0,1\}=[[:blank:]]\{0,1\}\).*/\1 newValue/g' file

Also to limit the number of occurences of those spaces, change limits in \\{0,1\\} and in case you accept any number of spaces,

sed -i 's/\(key[[:blank:]]*=[[:blank:]]*\).*/\1 newValue/g' file

Also, the same can be done with a little more simplicity with awk (well I think so):

newVal="your_new_value"
awk -F= -v newVal="$newVal" '/ *key *=/{$2="="newVal}{print}' file

To retain changes in file:

newVal="your_new_value"
gawk -i -F= -v newVal="$newVal" '/ *key *=/{$2="="newVal}{print}' file