quick script question

[M E Fieu]

Hi.. Need to ask you a simple script question,  I used the date command to get the yesterday web
log file using the following command echo ex`date -d yesterday +%y%m%d.log`  in Linux.  I want to
create a simple script to cat /home/IT/ex060530.log > kr.log using the following script but it is
not working.  May I know how do I put the output of echo ex`date -d yesterday +%y%m%d.log into cat
/home/IT/xxxx  > kr.log ?

[root@w2 krweblog3]# echo ex`date -d yesterday +%y%m%d.log`
ex060530.log

[root@w2 krweblog3]# vi krweblog.sh

#!/bin/sh
#
KRWEBLOG3= echo ex`date -d yesterday +%y%m%d.log`
cat /home/IT/$KRWEBLOG3 > kr.log

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[Todd Zullinger]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

M E Fieu wrote:
> Hi.. Need to ask you a simple script question,  I used the date
> command to get the yesterday web log file using the following
> command echo ex`date -d yesterday +%y%m%d.log`  in Linux.  I want to
> create a simple script to cat /home/IT/ex060530.log> kr.log using
> the following script but it is not working.  May I know how do I put
> the output of echo ex`date -d yesterday +%y%m%d.log into cat
> /home/IT/xxxx> kr.log ?
>
> [root@w2 krweblog3]# echo ex`date -d yesterday +%y%m%d.log`
> ex060530.log
>
> [root@w2 krweblog3]# vi krweblog.sh
>
> #!/bin/sh
> #
> KRWEBLOG3= echo ex`date -d yesterday +%y%m%d.log`
> cat /home/IT/$KRWEBLOG3> kr.log

Get rid of the echo, it's not needed.

KRWEBLOG3="ex`date -d yesterday +%y%m%d.log`

If you ever do have to run a few commands to create a variable, you
can use bash's command substitution to nest commands.  Instead of
using backquotes (`command`), you use $(command).

KRWEBLOG3=$(echo ex$(date -d yesterday +%y%m%d.log))

See the section on Expansion in the bash man page for more details.

- -- 
Todd        OpenPGP -> KeyID: 0xD654075A | URL: www.pobox.com/~tmz/pgp
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> f7lLilm/oUK89/qpt4hg
> =etmy
> -----END PGP SIGNATURE-----

[Mikkel]

M E Fieu wrote:
> Hi.. Need to ask you a simple script question,  I used the date command to get the yesterday web
> log file using the following command echo ex`date -d yesterday +%y%m%d.log`  in Linux.  I want to
> create a simple script to cat /home/IT/ex060530.log > kr.log using the following script but it is
> not working.  May I know how do I put the output of echo ex`date -d yesterday +%y%m%d.log into cat
> /home/IT/xxxx  > kr.log ?
>
> [root@w2 krweblog3]# echo ex`date -d yesterday +%y%m%d.log`
> ex060530.log
>
> [root@w2 krweblog3]# vi krweblog.sh
>
> #!/bin/sh
> #
> KRWEBLOG3= echo ex`date -d yesterday +%y%m%d.log`
> cat /home/IT/$KRWEBLOG3 > kr.log

For thing like this, I like to use something like:

KRWEBLOG=$(date -d yesterday +ex%y%m%d.log)
cat /home/IT/$KRWEBLOG3 > kr.log

KRWEBLOG will have the value of ex060530.log if I ran it now on my
system. Enclosing a command inside $() returns the output of the
command. You could also use:
KRWEBLOG=`date -d yesterday +ex%y%m%d.log`
but I find the $() format easyer to read.

Mikkel