Common shell commands #bash #find #sed

common-shell-commands.sh

#!/bin/bash

# bash for loop
for i in $(seq 10 $END); do
  echo $i
done

# 1.Iterate over collection
for i in a b c; do
  echo $i
done

# 2.Iterate over numeric range
for i in {1..5}; do
  echo $i
done

# 3.Iterate over files in directory
for filename in *; do
  echo $filename
done

# move files from folder to folder
for d in */; do
  echo "$d"
  mkdir -p ../_notes/$d
  mv $d/* ../_notes/$d
done

# rename file with folder name
for d in */; do
  echo "$d"
  a=$(ls "$d"/filename.*)
  echo $a
  b=$(echo $a | sed s://filename::)
  echo $b
  mv "$a" "$b"
done

# Bash Brace Expansion example. see gnu.org/software/bash/manual/html_node/Brace-Expansion.html
echo a{d,c,b}e #ade ace abe

# For loop to exeute some task multiple times
for i in Item1 Item2 ItemN; do
  bash ~/task.sh ${i}
done

for i in {1..10}
do
  wget https://static.generated.photos/vue-static/human-generator/poses/female/00$i.png
done

# Remove the line immediately after front matter
for filename in $TEMP/*; do
  echo $filename
  sed '8d' $filename >tmpfile
  mv tmpfile $filename
done

# Strip out all of the links of an HTML file in Bash or grep or batch and store them in a text file
# ref: https://stackoverflow.com/questions/21264626/how-to-strip-out-all-of-the-links-of-an-html-file-in-bash-or-grep-or-batch-and-s
sed -n 's/.*href="\([^"]*\).*/\1/p' file

# Batch process images
for file in *.PNG; do convert $file -resize 400 ../output/resized-$file; done

# Add prefix to filenames
# ref: stackoverflow.com/questions/208181/how-to-rename-with-prefix-suffix
for i in a b; do mv {,PREFIX_}$i; done

# Change all occurrences of word in file content in a folder
# sed beginner: changing all occurrences in a folder. see: stackoverflow.com/questions/905144/sed-beginner-changing-all-occurrences-in-a-folder
find . -type f -exec sed -i "s/foo/bar/g" {} \;

# Rename all files of the same name to another name in all subdirectories
find .  -name output.txt -type f -execdir mv -T output.txt output_modified.txt ';'

# Batch rename files in directory with date modified timestamp as prefix of the filename
# ref: https://unix.stackexchange.com/questions/43338/renaming-a-bunch-of-files-with-date-modified-timestamp-at-the-end-of-the-filenam
for f in *; do mv -- "$f" "$(date +%Y-%m-%d -r $f)-$f"; done

# Use git conbined with sed/awk to automate text processing tasks
eval "find app/ -type f -exec sed -i 's/target/replacement/g' {} \;"

git diff
echo -n "Here be dragons. Continue?"
read REPLY
if [[ "$REPLY" =~ ^[Yy]$ ]]
then
  git add .
  git cm "processing $1 complete"
fi

# add namespace to all models
find app/models/ -type f -exec sed -i "1 i module MyModule" {} \;
find app/models/ -type f -exec sed -i "$ a  end" {} \;

# you can also automate code indentation, see https://gist.github.com/goooooouwa/d5f40319ab7fb80a7fe4