[nycbug-talk] nifty(1)

[Henry M]

Wouldn't it be nice to just 'man nifty' and a have a large collection of
tricks?

One nifty trick with curl and awk:

Curl a website and print it's status code only if it's the code you are
looking for.

Example 1: (This will print 200.)
curl -sL -w "\n%{http_code}\n" "nycbug.org/" |
awk 'BEGIN { getline line } { print line; line=$0 } END { if (line ~/200/)
{print line;}}'


Example 2: (This will not print 404)
curl -sL -w "\n%{http_code}\n" "nycbug.org/" |
awk 'BEGIN { getline line } { print line; line=$0 } END { if (line ~/404/)
{print line;}}'

Useless? I say not!

~Henry

On Wed, Dec 14, 2011 at 6:13 PM, Isaac Levy <ike at blackskyresearch.net>wrote:

> On Dec 14, 2011, at 5:28 PM, Matthew Story wrote:
> > who's up next?
> This nifty(1) thread is a great idea!
>
> "The 3-finger Claw Technique"  The sweetest 3 functions, ever.
>
>  shout() { echo "$0: $*" >&2; }
>  barf() { shout "$*"; exit 111; }
>  safe() { "$@" || barf "cannot $*"; }
>
> I use these daily, they're extremely cross-platform friendly in any
> bourne-derived shell I've  used in the last 3 years.
>
>
> safexample.sh :
> --
> #!/bin/sh
>
> shout() { echo "$0: $*" >&2; }
> barf() { shout "$*"; exit 111; }
> safe() { "$@" || barf "cannot $*"; }
>
> # consider the following lines
> safe cd /some/dir
> safe tar xzvfp /my/big/tarball.tbz
>
> exit 0
> --
>
>
> In the above example, using 'safe' suddenly gives the user the following
> special powers:
>
> 1) if '/some/dir' does not exist, the script will safely exit before that
> un-tarring does any damage.
>
> 2) the actual 'directory does not exist' will return to stderr for the
> script, (as opposed to just telling us the useless fact that the enclosing
> script failed).
> Now bourne shell starts behaving like a modern language!  (ala Python/Ruby
> tracebacks, Perl errors, etc…)
>
> Additonally, if you 'exit 0' at the end, you can run non-safe operations,
> and always be guaranteed that if the shell exits, it was 'complete'.
> An example:
>
> # consider the following lines
> safe cd /some/dir
> tar xzvfp /my/big/tarball.tbz
>
> Now, safe was removed from the un-tar command, right?  So, imaging
> tarballs created by people using a Mac (with HFS+ and some
> filesystem-specific sticky bit somewhere in the filesystem which was tar'd
> up).
> Now, you un-tar it on some *BSD or other *NIX box, and tar complains as it
> goes- and exits non-zero.  One way to handle this, is to consider the tar
> 'reliable', and not use safe for it.
>
> Now, if we continue to be conscious of this simple safe/notsafe
> distinction with these scripts, they can be called by other safe scripts-
> and behave just like any respectable UNIX program!
>
> Now, consider this crontab entry:
> 1       3       *       *       *       someuser flock -k
> /tmp/safexample.lock /path/to/safexample.sh
>
> If it fails, (for bad perms, no tarball to unpack, etc…)  cron will
> actually have a reasonable message to email/log on failure!
>
>
> Thanks to the noble efforts of the Clan of the White Lotus, these 3
> functions originate during the late thirteenth century, around Guangzhou.
>  It is rumored these 3 functions took 15 years to boil down- I beileve that
> after mercilessly abusing them for the last 3 years myself…  (I'm not
> kididng about that part!)
>
> Attached, is another example with more bits.
>
>
>
> _______________________________________________
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> talk at lists.nycbug.org
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>
>
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