mikazz/BashSnippets

BashSnippets

Append to file

i.e.:

echo "hello world" >> my_file.txt

Redirect both stdout and stderr to a files

one file:

kill -l 1234 > killouterr.txt 2> &1

two files:

kill -l 1234 > killout.txt > killerr.txt

Conditionals

if [ -z "$string" ]; then
  echo "String is empty"
elif [ -n "$string" ]; then
  echo "String is not empty"
fi

File operations

Output the number of lines

wc -l

Remove first n lines from file

sed -i '1,n' file.txt

Reading lines

cat file.txt | while read line; do
  echo $line
done

Cut and find top 100 lines from file

file: dump.txt separator: ":"

cut -f 2 -d ":" dump.txt|sort|uniq -c|sort -r|head -n 100    

Loops

Basic for loop

for i in /etc/rc.*; do
  echo $i
done

Ranges

for i in {1..5}; do
    echo "Welcome $i"
done

With step size

for i in {5..50..5}; do
    echo "Welcome $i"
done

Functions

Defining functions

myfunc() {
    echo "hello $1"
}
# Same as above (alternate syntax)
function myfunc() {
    echo "hello $1"
}
myfunc "John"

Returning values

myfunc() {
    local myresult='some value'
    echo $myresult
}
result=$(myfunc)

Raising errors

myfunc() {
  return 1
}
if myfunc; then
  echo "success"
else
  echo "failure"
fi

Git

git commit && git push
git commit || echo "Commit failed"