Commands tagged validation (5)

  • On CentOS at least, date returns a boolean for the common date string formats, including YYYY-MM-DD. In the sample output, you can see various invalid dates returning 0 whereas a simple regex check would return 1 for the invalid dates. -d, --date=STRING display time described by STRING, not `now' The version of date on OS X does not appear to have this same option. Show Sample Output


    0
    if date -d 2006-10-10 >> /dev/null 2>&1; then echo 1; else echo 0; fi
    SteveGoossens · 2013-01-10 10:35:15 0
  • Validates and pretty-prints the content fetched from the URL. Show Sample Output


    11
    curl -s "http://feeds.delicious.com/v2/json?count=5" | python -m json.tool | less -R
    keimlink · 2010-03-24 09:15:12 1
  • Place the regular expression you want to validate between the forward slashes in the eval block. Show Sample Output


    4
    perl -we 'my $regex = eval {qr/.*/}; die "$@" if $@;'
    tlacuache · 2009-10-13 21:50:47 1
  • Using the standard numeric comparison but suppressing the STDERR output acts as the simplest way to check a value is numeric. See sample output for some examples. Show Sample Output


    0
    if [ "$testnum" -eq "$testnum" 2>/dev/null ]; then echo It is numeric; fi
    jgc · 2009-10-09 14:57:27 4
  • Quick and easy way of validating a date format of yyyy-mm-dd and returning a boolean, the regex can easily be upgraded to handle "in betweens" for mm dd or to validate other types of strings, ex. ip address. Boolean output could easily be piped into a condition for a more complete one-liner.


    -1
    echo 2006-10-10 | grep -c '^[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]$'
    rez0r · 2009-05-11 22:18:43 3

What's this?

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

Share Your Commands



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: