Fringe Division

Appearance

Bash ​

Flow control ​

bash
# loop
for file in *.txt; do cat $file; done

# if-else
if [ $(whoami) = 'root' ]; then
 echo "You are root"
else
 echo "You are not root"
fi

base64 ​

bash
# base64 binary decode
echo "$myImgStr" | base64 -d > image2.jpg

jq ​

bash
# string -> json
jq '.c | fromjson | .id' myFile.json


# json -> string
echo '{ "foo": [ "bar", "baz" ] }' | jq tostring

openssl ​

bash
# generate password
docs openssl rand -base64 24

rsync ​

bash
# copy with progress bar
rsync -ah --progress source-file destination-file

# move files
--remove-source-files

# ignore folder
rsync -avm --exclude='node_modules' --progress $HOST:$PATH $TARGET/

sed ​

bash
# replace string in text file
sed -i 's/old-text/new-text/g' input.txt

## can also use `#` as separator
sed -i.bak 's#$HOME#/home/runner/work#' scripts/docker-pytest.sh

## osx
sed -i .bak 's/old-text/new-text/g' input.txt

## recursive
grep -rl old-text . | xargs sed -i '' 's/old-text/new-text/g'

split ​

bash
split -l 300 file.txt new
split -b 500m httpd.log

xargs ​

bash
ls file_* | xargs -J {} mv {} temp/

Cookbook ​

Generate random number ​

bash
r=$(( $RANDOM % 1000 + 1 ))

Check if file exists ​

bash
if [ -f ".env" ]; then
 source ./.env
else
 echo "env doesn't exist!"
    exit 1
fi

Loop list from a file ​

bash
IFS=$'\n' images=($(cat need_to_process_files.txt))
for i in ${images[@]}
do
    aws s3 cp "s3://$BUCKET_NAME/$i" images/
done

Run script every x interval ​

bash
while true;
do
    echo "hello";
    sleep 300; # 5 minutes
done;

Append multi-line to file ​

bash
cat <<EOF >>$FILE
foo
bar
baz
EOF