01-13-2012
Hi,
Last question:
you may start with 'Linux Hands on Guide', you can find it on tldp.org; it's not specifically about shell scripting, but has useful exercises at the end of each chapter that may be useful for you.
see ya
fra
---------- Post updated at 14:55 ---------- Previous update was at 14:55 ----------
Answer to first question:
$i gets the value of the first word (that is, set of contiguous, non space-interleaved characters) in the file.
in order to loop you don't have to modify $i. $i in the specific example is not a counter.
Second question: it' not very clear to me what are the starting conditions (what are the input data or files).
This User Gave Thanks to frappa For This Post:
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LEARN ABOUT OPENSOLARIS
foreach
foreach(1T) Tcl Built-In Commands foreach(1T)
__________________________________________________________________________________________________________________________________________________
NAME
foreach - Iterate over all elements in one or more lists
SYNOPSIS
foreach varname list body
foreach varlist1 list1 ?varlist2 list2 ...? body
_________________________________________________________________
DESCRIPTION
The foreach command implements a loop where the loop variable(s) take on values from one or more lists. In the simplest case there is one
loop variable, varname, and one list, list, that is a list of values to assign to varname. The body argument is a Tcl script. For each
element of list (in order from first to last), foreach assigns the contents of the element to varname as if the lindex command had been
used to extract the element, then calls the Tcl interpreter to execute body.
In the general case there can be more than one value list (e.g., list1 and list2), and each value list can be associated with a list of
loop variables (e.g., varlist1 and varlist2). During each iteration of the loop the variables of each varlist are assigned consecutive
values from the corresponding list. Values in each list are used in order from first to last, and each value is used exactly once. The
total number of loop iterations is large enough to use up all the values from all the value lists. If a value list does not contain enough
elements for each of its loop variables in each iteration, empty values are used for the missing elements.
The break and continue statements may be invoked inside body, with the same effect as in the for command. Foreach returns an empty string.
EXAMPLES
The following loop uses i and j as loop variables to iterate over pairs of elements of a single list. set x {} foreach {i j} {a b c d e f}
{
lappend x $j $i } # The value of x is "b a d c f e" # There are 3 iterations of the loop.
The next loop uses i and j to iterate over two lists in parallel. set x {} foreach i {a b c} j {d e f g} {
lappend x $i $j } # The value of x is "a d b e c f {} g" # There are 4 iterations of the loop.
The two forms are combined in the following example. set x {} foreach i {a b c} {j k} {d e f g} {
lappend x $i $j $k } # The value of x is "a d e b f g c {} {}" # There are 3 iterations of the loop.
SEE ALSO
for(1T), while(1T), break(1T), continue(1T)
KEYWORDS
foreach, iteration, list, looping
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Availability | SUNWTcl |
+--------------------+-----------------+
|Interface Stability | Uncommitted |
+--------------------+-----------------+
NOTES
Source for Tcl is available on http://opensolaris.org.
Tcl foreach(1T)