tricks.md

Shell rename

Rename part of a filename with discrete shell expansion:

mv /long/annoying/path/{file,stuff}.txt # rename to stuff
mv /long/annoying/path/{,the-}file.txt  # adds prefix

Private key num bits

How to figure out how many bits your id private key. https://security.stackexchange.com/a/42272/135955

openssl rsa -text -noout -in id_rsa

Generate random string

Generate a random password. https://unix.stackexchange.com/a/306107/162041

openssl rand -hex 12

Copy ssh key to remote box

Copy an ssh key to a box, inluding adding to authorized_keys.

ssh-copy-id -n -f -i ~/.ssh/mykey user@host

Keep all of one side git conflict

Choose all of one or another during a git conflict. http://gitready.com/advanced/2009/02/25/keep-either-file-in-merge-conflicts.html

git checkout --ours FILE
git checkout --theirs FILE

Undo git commit ammend

Undo a git commit --amend https://stackoverflow.com/a/1459264/2601179

git reset --soft HEAD@{1} && git reset

Write to file from shell

Write several lines to a file in a script. Note that the EOF is just an arbitrary string.

cat > FILE <<<EOF
some
lines
about
stuff
EOF

Elasticsearch aggregations

Get aggregations of some field in Elasticsearch.

d = requests.get('http://localhost:9200/INDEX/doc/_search', json={
  'size': 0, 'aggregations': {'NAME': {'terms': {'size': 32, 'field': 'FIELD'}}},
}).json()
[(b['doc_count'], b['key']) for b in d['aggregations']['NAME']['buckets']]

Inspect a command or alias

Do command -V FOO to display what an alias is set to or, whether it's a function instead. To see how that custom function is defined as do declare -f FOO.

Loop over values with arg assignment

One can loop and assign over multiple return values or tuples like in shell like

# Create a toy CSV file.
cat > /tmp/foo.csv <<EOF
letter,number,fruit
a,1,apple
b,2,orange
c,3,pear
EOF

# Skip first row, and split by comma.
awk 'NR>1' < /tmp/foo.csv | while IFS=, read col1 col2 col3; do
  echo "ROW: $col1 $col2 $col3"
done | column -t

List all untracked files in git

# https://stackoverflow.com/a/3801554/2601179
git ls-files --others --exclude-standard

See codes for certain key-presses

For example, cat followed by \n, , \n, , \n, , will allow you to see which terminal sequences correspond to those key presses [1]:

% cat
^[[1;3D

^[[1;3C

[1] https://stackoverflow.com/a/12403798/2601179

Strip trailing whitespace

Here's two different ways to do it:

echo " padded " | xargs
echo " padded " | awk '{$1=$1;1}'

More flexible watch

Another more flexible alternative to sleep is to do something like this:

while sleep 2; do foobar; done