Shell Commands

1. Find file in a directory

find <directory> -name "<file name>"
find <directory> -regex "<regex>"

2. Search file by keyword/regex

grep -R "<keyword>" <directory>

3. Retrieve matching text in a file

grep -oEi '<regex>' <directory>

4. Join multiple lines into one line with delimeter

<source of multiple lines> | paste -s -d "<delimiter>"
<source of multiple lines> | perl -pe 's/\n$/ <delimeter text> /'

5. Curl with HTTP authentication

curl -u <username>:<password> <url>

6. To redirect both STDOUT and STDERR to the same place, use the >& symbol. To redirect STDOUT only, use 1>. To redirect STDERR only, use 2>.
7. Separate lines into fields according to delimiter and get selected portion

<source> | cut -d '<delimiter>' -f 1,3-5