But if for some reason sort fails (for e.g: if the /tmp fir is full) the above command returns 0 as the answer. I am not able to catch the status of each individual command in the pipe.
So the code I had before is:
What I want is, if sort fails, I should be able to catch it.
Therefore I had to implement pipe, to get the status of each individual calls.
So now, based on your program above, I have the following code:
This works great !!!
However, what I want is to capture the output of sort | uniq | wc in a variable (like I did before) and not print it on stdout.
Hello again... I have a request from another department to list for them all the columns and tables we use in this certain database. I have spooled the oracle stored procedured into 1 file. I need a way to write out parts of that file. The criteria is to to start the block to be written when... (0 Replies)
suppose by writing this code
"$ /sbin/ifconfig eth0| grep 'inet addr:' "
i've got this output
"inet addr:192.168.2.1 Mask:255.255.255.0"
now if i want to see the output like this
"IP address: 192.168.2.1
Subnet Mask: 255.255.255.0"
what is the code should be?
can anyone... (3 Replies)
hi
i am studying unix with c language ,and completely new to this .I have question about how to pass the control from one program file to another.My first program has the main process and it should go into the second program where i can create six processes with also the usage of pipes to... (3 Replies)
hi fndz.
Can you please help me with the code if I call a stored procedure from my shell script and stored procedure returns a cursor,
cursor output should be saved to a file (3 Replies)
1. The problem statement, all variables and given/known data:
Write a script that will perform the grep command on a user defined file and a user defined pattern
2. Relevant commands, code, scripts, algorithms:
must use grep command (that is the only piece of information that was given)
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Hi guys, I'm modifying an old f77 code using vi. I'm modifying the code remotely from my windows machine using xming using vi. I'm using tabs to move past the first 6 columns of the code and to keep my loops and if statements neat, but when I hit the tab key, vi displays a big red block which is... (7 Replies)
Hi there,
I have two questions. First, I was wondering how to use sed to remove two header lines or two tail lines. Here I just do the same operation twice...I'm sure there is a better way. Second, and more importantly, is there a better way to have these operations use files other than... (5 Replies)
Hi Friends,
I am back with small issue which i tried thinking but could not get much!!!!
issue here is..i m using kind of extraction query using perl code in that i do sort with few number of csv files. each of them will be around 50 to 100 M size.
sometime i get following error message... (1 Reply)
Folks -
Firstly, I do apologize that my first post here is a question. I am quite familiar with UNIX since our application is running on it. We are trying to automate a few things on our end and I am challenged with a task in hand that requires UNIX scripting. I am totally a newbie in UNIX... (4 Replies)
Hi,
i need a string that take from a log file just two words (ngwan0) and his related ip address and then execute 2 commands in a shell. Any ideas where to start?
Thanks (3 Replies)
Discussion started by: Board27
3 Replies
LEARN ABOUT MOJAVE
sort5.18
sort(3pm) Perl Programmers Reference Guide sort(3pm)NAME
sort - perl pragma to control sort() behaviour
SYNOPSIS
use sort 'stable'; # guarantee stability
use sort '_quicksort'; # use a quicksort algorithm
use sort '_mergesort'; # use a mergesort algorithm
use sort 'defaults'; # revert to default behavior
no sort 'stable'; # stability not important
use sort '_qsort'; # alias for quicksort
my $current;
BEGIN {
$current = sort::current(); # identify prevailing algorithm
}
DESCRIPTION
With the "sort" pragma you can control the behaviour of the builtin "sort()" function.
In Perl versions 5.6 and earlier the quicksort algorithm was used to implement "sort()", but in Perl 5.8 a mergesort algorithm was also
made available, mainly to guarantee worst case O(N log N) behaviour: the worst case of quicksort is O(N**2). In Perl 5.8 and later,
quicksort defends against quadratic behaviour by shuffling large arrays before sorting.
A stable sort means that for records that compare equal, the original input ordering is preserved. Mergesort is stable, quicksort is not.
Stability will matter only if elements that compare equal can be distinguished in some other way. That means that simple numerical and
lexical sorts do not profit from stability, since equal elements are indistinguishable. However, with a comparison such as
{ substr($a, 0, 3) cmp substr($b, 0, 3) }
stability might matter because elements that compare equal on the first 3 characters may be distinguished based on subsequent characters.
In Perl 5.8 and later, quicksort can be stabilized, but doing so will add overhead, so it should only be done if it matters.
The best algorithm depends on many things. On average, mergesort does fewer comparisons than quicksort, so it may be better when
complicated comparison routines are used. Mergesort also takes advantage of pre-existing order, so it would be favored for using "sort()"
to merge several sorted arrays. On the other hand, quicksort is often faster for small arrays, and on arrays of a few distinct values,
repeated many times. You can force the choice of algorithm with this pragma, but this feels heavy-handed, so the subpragmas beginning with
a "_" may not persist beyond Perl 5.8. The default algorithm is mergesort, which will be stable even if you do not explicitly demand it.
But the stability of the default sort is a side-effect that could change in later versions. If stability is important, be sure to say so
with a
use sort 'stable';
The "no sort" pragma doesn't forbid what follows, it just leaves the choice open. Thus, after
no sort qw(_mergesort stable);
a mergesort, which happens to be stable, will be employed anyway. Note that
no sort "_quicksort";
no sort "_mergesort";
have exactly the same effect, leaving the choice of sort algorithm open.
CAVEATS
As of Perl 5.10, this pragma is lexically scoped and takes effect at compile time. In earlier versions its effect was global and took
effect at run-time; the documentation suggested using "eval()" to change the behaviour:
{ eval 'use sort qw(defaults _quicksort)'; # force quicksort
eval 'no sort "stable"'; # stability not wanted
print sort::current . "
";
@a = sort @b;
eval 'use sort "defaults"'; # clean up, for others
}
{ eval 'use sort qw(defaults stable)'; # force stability
print sort::current . "
";
@c = sort @d;
eval 'use sort "defaults"'; # clean up, for others
}
Such code no longer has the desired effect, for two reasons. Firstly, the use of "eval()" means that the sorting algorithm is not changed
until runtime, by which time it's too late to have any effect. Secondly, "sort::current" is also called at run-time, when in fact the
compile-time value of "sort::current" is the one that matters.
So now this code would be written:
{ use sort qw(defaults _quicksort); # force quicksort
no sort "stable"; # stability not wanted
my $current;
BEGIN { $current = sort::current; }
print "$current
";
@a = sort @b;
# Pragmas go out of scope at the end of the block
}
{ use sort qw(defaults stable); # force stability
my $current;
BEGIN { $current = sort::current; }
print "$current
";
@c = sort @d;
}
perl v5.18.2 2013-11-04 sort(3pm)