topic Re: Shell script filename expansion in Operating System - HP-UX

Shell script filename expansion

Sebastien Masson — Mon, 18 Feb 2002 17:56:30 GMT

Hi all,

After a few search in the forum, I would like to do a wrapper for a unix command and I want to pass /*/zaza as script parameter and the script resend this parameter to the unix command without expanding the *....

Please help wanted....

Re: Shell script filename expansion

Tom Danzig — Mon, 18 Feb 2002 18:02:44 GMT

Add a backslash prior to the * to avoaid shell expanding the *.

/\*/zaza

Re: Shell script filename expansion

Luc Bussieres — Mon, 18 Feb 2002 18:06:07 GMT

Sebastien,

What you need to do is quote the parameter, all the time. For example if your script is named test. The user will have to type:

test "/*/params"

This will make sure that the shell won't expand it. Then in the script you will also quote the parameter when you want to resend it to a unix command:

test2 "$1"

Luc

Re: Shell script filename expansion

Volker Borowski — Mon, 18 Feb 2002 18:08:44 GMT

Hi,

you need to stop the shell from evaluating the wildcard, so the script must be called with quotes.

script '/*/zaza'

inside the script $1 will be '/*/zaza' WITHOUT the quotes.

Since the line in your script will be evaluated by a shell again, you need to re-insert quotes. But plainly reinserting quotes might hinder the shell from evaluating the $-sign to expand the parameter so you need to use double quoutes, therefore the call inside your script needs to be

call_inside_script "$1"

See the following to explain the quotes:

# export HELLO='*'

# echo $HELLO
Mail SD_CDROM a adabas b bin c cn_tmp dev etc home lib lost+found lsof-4.55-sd-11.00.depot mapvg01.map net nfs_mount omni omnicopy r

# echo '$HELLO'
$HELLO

# echo "$HELLO"
*

Hope this helps
Volker

Re: Shell script filename expansion

Sebastien Masson — Mon, 18 Feb 2002 18:17:26 GMT

Ok I think some few cmd output needed:

----------------------------
My sample script: zazou.sh
----------------------------
#!/bin/sh
echo $1
----------------------------

Sure: echo /\*/zaza
return: /*/zaza

But

./zazou.sh /\*/zaza
return: /a01/zaza /a02/zaza /a03/zaza

Re: Shell script filename expansion

T. M. Louah — Mon, 18 Feb 2002 18:19:16 GMT

BTW did u try .. # export H=\/\*\/zaza
# echo $H should give
/*/zaza

g`d luck

Re: Shell script filename expansion

Volker Borowski — Mon, 18 Feb 2002 18:26:19 GMT

Yes Sebastien,

that is exactly correct.
If you want the script to display

/*/zaza

You need to use

echo "$1"

inside the script.

In
echo $1
the parameter $1 will be evaluated and after that the wildcard will be expanded.

Volker

Re: Shell script filename expansion

Deepak Extross — Tue, 19 Feb 2002 03:54:34 GMT

Are you looking for "set -f"?

Doing a
set -f
will turn off filename expansion. It will remained turned off till you issue a
set +f

Hope this helps.

Re: Shell script filename expansion

Peter Kloetgen — Tue, 19 Feb 2002 06:54:25 GMT

Hi Sebastien,

quoting (masquerading) of special characters isn't as trivial as people often think! But if you know the rules, it can be very simple:

'string_to_quote'--> quotes every special character within...

"string_to_quote" -->quotes some special characters, but others are not quoted, within there is continuing variable substitution and command substitution, so the $- character and the ``backticks are not quoted!

\special_character -->quotes the character which is following directly, only one character!

The next thing you need to know is, how a shell interpretes a command line before it is executed:

the shell takes a look at the whole command line and seeks for special characters to be interpreted, like backticks for command substitution or a $-character for variable substitution. It is easy to find out how the command line looks like after interpreting but before execution:

set -o xtrace
command_line
set +o xtrace

set -o xtrace turns on a debugging mode which shows you the command line after interpretation with a + character in front of the line. Then you see the output of the command line.
set +o turns of the debugging mode. These two lines at the beginning and at the end of your scripts can be very helpful when searching for errors!

example:
var=value
set -o xtrace
echo '$var' "$var" \$var (RETURN)
+ echo $var value $var
$var value $var

Allways stay on the bright side of life!

Peter