Hide

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/

Get involved!

You can sign-in using OpenID credentials, or register a traditional username and password.

OpenID
or
Sign in Register

First-time OpenID users will be automatically assigned a username which can be changed after signing in.

Hide

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

Hide

News

2011-03-12 - Confoo 2011 presentation
Slides are available from the commandlinefu presentation at Confoo 2011: http://presentations.codeinthehole.com/confoo2011/
2011-01-04 - Moderation now required for new commands
To try and put and end to the spamming, new commands require moderation before they will appear on the site.
2010-12-27 - Apologies for not banning the trolls sooner
Have been away from the interwebs over Christmas. Will be more vigilant henceforth.
2010-09-24 - OAuth and pagination problems fixed
Apologies for the delay in getting Twitter's OAuth supported. Annoying pagination gremlin also fixed.
Hide

Tags

Hide

Functions

Hide

Credits

Site by David Winterbottom (user root).

Use ping to test if a server is up

Terminal - Use ping to test if a server is up
if [ "$(ping -q -c1 google.com)" ];then wget -mnd -q http://www.google.com/intl/en_ALL/images/logo.gif ;fi
2010-03-23 04:15:03
User: alf
Functions: wget
-1
Up
Down
Use ping to test if a server is up

Bash scrip to test if a server is up, you can use this before wget'ing a file to make sure a blank one isn't downloaded.

Add to favourites | Report as malicious

Alternatives

There are 2 alternatives - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

If you're not going to have an "else" clause, you can shorten that to:

[ "$(ping -q -c1 google.com)" ] && wget ...

'if' works by using the '[' (test) command, but you can use it directly.

Comment by flatcap 165 weeks and 1 day ago

Alternatively (not as pretty):

ping -c1 google.com > /dev/null && wget ...
Comment by flatcap 165 weeks and 1 day ago

Wouldn't it be better to use curl -I to check the headers for a 200 OK? Just because a machine is responding to pings, that doesn't mean that the webserver is up.

Comment by eightmillion 165 weeks ago

I don't have the means to test this example at the moment, but I believe it should work.

curl -Is google.com 2>&1 | grep -q "200 OK" && wget ...
Comment by eightmillion 165 weeks ago

Great alternatives, I'll have to give these a try!

Comment by alf 165 weeks ago

'if' expects a command. '[' is actually a program, not part of the shell. So you can actually just do

if ping -q -c1 google.com; then ...
Comment by recursiverse 165 weeks ago

No need for the 'then' or even an 'else', just use && or ||

e.g.:

ping -c1 host.com > /dev/null && echo "YES" || echo "NO"

This is the equivalent of:

if ping -c1 host .com > /dev/null then echo "YES" else echo "NO" fi
Comment by finkployd 136 weeks and 6 days ago

Your point of view

You must be signed in to comment.

Related sites and podcasts