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Question about $*

 
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# 1  
Old 10-27-2014
Question about $*
Hi,

I have shell scrit code like below, but I have need few clarification on this. I have explained my understanding and doubts after this code.

Code:
abcd()
{
        print  $(date +%y%m%d:%H%M%S) "$*"
}

exec >> /root/file1.log 2>&1

My understanding is abcd() is a function it print the current date, but I dont understand what is the purpose of"$*"

exec >> will execute above print date abcd function and send the error and o/p under .log file

Please correct me if my understanding is wrong.
Last edited by stew; 10-27-2014 at 07:44 AM..
# 2  
Old 10-27-2014
$* makes ALL positional parameters to THIS (not the main shell but the actual) function available; man bash:
Quote:
Special Parameters
The shell treats several parameters specially. These parameters may only be referenced; assignment to them is not allowed.
* Expands to the positional parameters, starting from one. When the expansion is not within double quotes, each positional
parameter expands to a separate word. In contexts where it is performed, those words are subject to further word splitting
and pathname expansion. When the expansion occurs within double quotes, it expands to a single word with the value of each
parameter separated by the first character of the IFS special variable. That is, "$*" is equivalent to "$1c$2c...", where c
is the first character of the value of the IFS variable. If IFS is unset, the parameters are separated by spaces. If IFS is
null, the parameters are joined without intervening separators.
exec >> will NOT call above function but replace the current shell with the command given after having prepared all redirections. If no command is given, the current shell continues with the redirections applied.
# 3  
Old 10-27-2014
Sadly your function will fail because there is no builtin statement called print ...

It should be printf instead.

---------- Post updated at 11:19 AM ---------- Previous update was at 11:08 AM ----------
EDIT:

Using CygWin as a command line demo and using the inverted commas correctly...
Code:
AMIGA:~> abcd() { printf "$(date +%y%m%d:%H%M%S) $*"; }
AMIGA:~> abcd Hi, my name is Baz...
141027:111657 Hi, my name is Baz...AMIGA:~> _

Last edited by wisecracker; 10-27-2014 at 08:19 AM.. Reason: See above...
# 4  
Old 10-27-2014
Quote:
Originally Posted by wisecracker
Sadly your function will fail because there is no builtin statement called print ...
It certainly does, but only in a very few shells, one of those strange ksh things. And that's not the way you should be using printf, either. Never cram unknown text into the command string, use "%s" "string"
 
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