'BASH - Replace text in 'ini' file using variables

I'm expecting this to be an easy one for someone (alas not me!).

Using a bash script, I want to replace a value in a config file '/etc/app/app.cfg' (ini style), using variables for both search and replace.

The Value Name and Value I wish to update (note the space either side of the equals:

LOGDIR = /etc/app/logs

I have defined the following in the bash script:

# Get existing LogDir value 
CURRENT_LOGDIR=$(grep 'LogDir =' /pathtofile | sed 's/LogDir *= *//g')

# Set New LogDir
LOGDIR=/mnt/eft/fs1/logs

# Update LogDir if different
if [[ -d $(echo $CURRENT_LOGDIR) != $LOGDIR ]] ; then
  # Update LogDir value:
  **bash command - I need help with !**
fi

I have tried many combinations with sed, to no avail, hence asking this question.

Things I've tried:

echo "LogDir = $LOGDIR" | sed '#s/$CURRENT_DIR/$LOGDIR/#g' /etc/app/app.cfg
sed -i '/#/!s/\(LogDir[[:space:]]*=[[:space:]]*\)\(.*\)/\1$LOGDIR#/g' /etc/app/app.cfg
sed -i 's/LogDir[[:space:]]=.*/LogDir = {LOGDIR}/' /etc/app/app.cfg
sed -i "s/^LogDir[[:space:]]*=.*/LogDir=$LOGDIR/}" /etc/app/app.cfg
sed -i '/#/!s/\(LogDir[[:space:]]*=[[:space:]]*\)\(.*\)/\1"$LOGDIR"/' /etc/app/app.cfg

Desired output:

Update LogDir value in /etc/app/app.cfg

For example:

LogDir = /mnt/eft/fs1/logs

bashsed


Solution 1:[1]

What is that } doing on the end? Looks like a typo.

sed "s/^LogDir[[:space:]]*=.*/LogDir=$LOGDIR/" /etc/app/app.cfg

And sed edit file in place

Solution 2:[2]

Using sed

$ LOGDIR=/mnt/eft/fs1/logs
$ sed -i.bak "s|\([^=]*=[[:space:]]\).*|\1$LOGDIR|" /etc/app/app.cfg
$ cat /etc/app/app.cfg
LOGDIR = /mnt/eft/fs1/logs

Solution 3:[3]

How about this:

awk '$1 == "LogDir" {print "LogDir = /mnt/eft/fs1/logs"; next} {print}' old_configuration_file >new_configuration_file

The first awk clause replaces the old LogDir entry by the new one, and the second clause passes the other lines through unchanged.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 KamilCuk
Solution 2 HatLess
Solution 3 user1934428

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