Last Updated: 2024-04-26

Sed

How to run multiple substitutions

Just separate them by ; in the same sed command string.

$ echo "2 + 2 = foo_bar" | sed 's/+/-/g; s/_/\&/g';
# 2 - 2 = foo&bar

How to substitute a line in package.json file in place using regex

Say the original line is

{
  "database": "bitbucket:someone/database#0.0.1"
}

sed -i '' 's/database#[0-9]*\.[0-9]*\.[0-9]*/database#0.0.2/g' filename

Explanation:

• The -i '' bit makes the edit happen in place. Note that this is a separate pair of quotation marks to the one in the substitution command
• We use [0-9] for digits because \d is not supported in sed

Print just the 2nd line from piped input

The base amount is sed '2p'. But the problem with this is that it also shows all the original input:

ps aux | grep gunicorn | sort -k 2 -t " " | sed '2p'
jackkinsella     65762   0.0  0.1 408897152  35200 s004  S+    2:43PM   0:00.23 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     65763   0.1  0.5 410154144 182496 s004  S+    2:43PM   0:02.31 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     65763   0.1  0.5 410154144 182496 s004  S+    2:43PM   0:02.31 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     65764   0.2  0.5 410155168 182688 s004  S+    2:43PM   0:02.10 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     65765   0.1  0.5 410153120 181904 s004  S+    2:43PM   0:02.65 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     65766   0.2  0.5 410154144 183648 s004  S+    2:43PM   0:02.30 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4
jackkinsella     66390   0.0  0.0 408628368   1648 s001  S+    2:46PM   0:00.00 grep --color=auto --exclude-dir=.bzr --exclude-dir=CVS --exclude-dir=.git --exclude-dir=.hg --exclude-dir=.svn --exclude-dir=.idea --exclude-dir=.tox gunicorn
 ~/Code/mm/morphmarket   master ●  ps aux | grep gunicorn | sort -k 2 -t " " | sed -n '2p'
jackkinsella     65763   0.1  0.5 410154144 182496 s004  S+    2:43PM   0:02.34 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4

To suppress this -- which you probably always want -- you need the -n flag.

 ps aux | grep gunicorn | sort -k 2 -t " " | sed -n '2p'
jackkinsella     65763   0.1  0.5 410154144 182496 s004  S+    2:43PM   0:02.26 /Users/jackkinsella/.virtualenvs/morphmarket/bin/python /Users/jackkinsella/.virtualenvs/morphmarket/bin/gunicorn mysite.asgi:application --pythonpath mysite --timeout 15 --max-requests 10000 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 4