sed, awk command line

1. Insert text from begining and special line (from line >= 57) with awk

• awk 'FNR>=57,$0="allow "$0{print}' /etc/nginx/akamai_https.conf > test2.txt
• sed -i -e 's/^/text\ to \ insert/g' filename

2. Replace all IP "xxx.xxx.xxx.xxx;" => "xxx.xxx.xxx.0/24;"

• sed -e 's/\.[0-9]\+;/\.0\/24;/g' /tmp/ips.txt > /tmp/new_ips.txt

    Here is content in file:

    access_log /var/log/test.log;

    I want to insert before the ; character

• sed -i -e "s/\(access_log.*.log\)\(;\)/\1\ combined\ if\=\$loggable\2/g" filename.txt

3. Replace string in all file in dir

• ls -1 <dir> | xargs -n1 -i%f sed -i -e 's/old_string/new_string/g' '%f'

4. Sed with variable with forward slash in shell script

• vari1=/Users/huytn/test
• sed -i -e "s/old_string/${vari1//\//\\/}/g" /path/to/file