Date: Fri, 01 Feb 2002 17:24:46 -0330 From: Paul David Fardy <pdf@morgan.ucs.mun.ca> To: "Crist J. Clark" <cristjc@earthlink.net> Cc: <questions@FreeBSD.ORG>, Eric Six <erics@sirsi.com> Subject: Re: Perl question... Message-ID: <200202012054.g11KslkB001080@plato.ucs.mun.ca>
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Eric Six <erics@sirsi.com> wrote:
>> I have found ways to append lines to the file, but not to create a new
>> one at the very beginning. Also, any ideas on how to automate doing
>> this to all the files in each dir?
"Crist J. Clark" <cristjc@earthlink.net> wrote:
> ed(1) man. man ed.
>
> for FILE in $DIR; do
> ed $DIR/$FILE <<"EOF"
> 1i
> $TTL value
> .
> wq
> EOF
> done
I've been using Perl so much, I've forgotten some of my shell rules.
I tested this code because I thought "$TTL" would result in the
expansion of an undefined variable TTL. In Perl, it _would_ be a
problem. In sh, it's fine.
But I think I'll still add a few notes.
> for FILE in $DIR; do
> ed $DIR/$FILE <<"EOF"
This should, I think, be
for file in *; do
ed $file <<"EOF"
or
for file in */*; do
ed $file <<"EOF"
Caveat: This is the syntax for the Bourne shell and its descendents/clones.
It won't work in C Shell or its descendents/clones. Put the code in a
file and run it with /bin/sh.
Caveat: Some implementations of /bin/ed do not recognize "wq". It's
more portable to use:
...
1i
$TTL value
.
w
q
i.e. separating the wq into 2 commands. (Bourne shell Tru64 UNIX doesn't
understand "wq".)
TMTOWTDI - There's more than one way to do it:
for file in *; do
perl -lp -i.bak -e 'print q($TTL 86400) if $. == 1' $file
done
This has one advantage: the original files are saved as filename.bak.
And it has one disadvantage: while the man page suggests "-i" means
"in-place", it's not really. The original file remains with a new
name; a new file is created and the protection and ownership of that
file are determined by the identity and the umask of the user running
this code.
Perl opts:
-e EXPR -- supplies Perl expression
-l -- add newline to every print (no need of \n)
-p -- wraps EXPR: "while (<>) { EXPR } continue { print }"
-i.bak -- non-quite in-place (keep old files as "filename.bak")
Assuming you've put your zone files (and only you zone files) in a
subdirectory, you can run
find /var/named/master -type f | \
xargs perl -lp -i.bak \
-e 'print q($TTL 86400) if $. == 1; close ARGV if eof'
The last bit of code has the effect of resetting "$." at the end of
each file.
Paul Fardy
--
BSD's date has 'date -r', but many UNIX systems don't. One of my
favourite "perl -le" expressions converts UNIX seconds to date:
The log file say time=1012596293. When was that?
perl -le 'print scalar localtime 1012596293'
Your password expires in 90 days. When is that?
perl -le 'print scalar localtime(time + 90*86400)'
(or 90*24*60*60) :-)
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