02-04-2013
Thanks a ton to you both ( neutronscott and Scrutinizer ), you guys got crazy skills .....
BTW, I am using Korn Shell.
To be very honest , I havent been into Shell scripting for a long period of time, but am keen to know how each of yours codes work .
@neutronscott----firstly what does ${a} in the expression "%0${a}d" stand for , and how different is it from using a blatant "%0$ad" or something like "%0'$a'd"
What I meant to ask is the significance of the {} while invoking a shell variable ?
@Scrutinizer---- I have to admit I dont even have any questions to ask BECAUSE I COULDNT MAKE THE HEADS OR TAILS OF WHAT YOU WROTE, but it works magic .
Could you please explain what your code does and the significance of "*" in the printf command ?
Thank you guys,
Kumarjit.
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expr(1) General Commands Manual expr(1)
Name
expr - evaluate expressions
Syntax
expr arg...
Description
The arguments are taken as an expression. After evaluation, the result is written on the standard output. Each token of the expression is
a separate argument.
The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped.
expr | expr Yields the first expr if it is neither null nor 0. Otherwise yields the second expr.
expr & expr Yields the first expr if neither expr is null or 0. Otherwise yields 0.
expr relop expr The relop is one of < <= = != >= > and yields 1 if the indicated comparison is true, '0' if false. The comparison is
numeric if both expr are integers, otherwise lexicographic.
expr + expr
expr - expr
Yields addition or subtraction of the arguments.
expr * expr
expr / expr
expr % expr
Yields multiplication, division, or remainder of the arguments.
expr : expr The matching operator compares the string first argument with the regular expression second argument; regular expres-
sion syntax is the same as that of The (...) pattern symbols can be used to select a portion of the first argument.
Otherwise, the matching operator yields the number of characters matched ('0' on failure).
( expr ) parentheses for grouping.
Examples
The first example adds 1 to the Shell variable a:
a=`expr $a + 1`
The second example finds the file name part (least significant part) of the pathname stored in variable a,
expr $a : '.*/(.*)' '|' $a
Note the quoted Shell metacharacters.
Diagnostics
The command returns the following exit codes:
0 The expression is neither null nor '0'.
1 The expression is null or '0'.
2 The expression is invalid.
See Also
ed(1), sh(1), test(1)
expr(1)