10 More Discussions You Might Find Interesting
1. UNIX for Beginners Questions & Answers
hello all
im new to unix and when i use below script i get an error :
#! /bin/bash
Echo -e "enter the name of the file : \c"
read file_name
if
then
echo "$file_name found"
else
echo "$file_name not found"
fi
running the script i get below error :
$ ./hello (26 Replies)
Discussion started by: Ibrahims1
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Hi folks,
I have a scenario to convert the update statements into insert statements using shell script (awk, sed...) or in database using regex.
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${PFILE}.backupfile
Please tell me what the above statement means? (1 Reply)
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Hi all,
After so many tries and searching online for ideas, I had trouble accomplishing this. Is it possible to do something like this in KSH to run an if statement on a return code?
Unfortunately the code below fails... Would anyone know how to fix the below attempt?
if "$`{pkginfo... (3 Replies)
Discussion started by: chatguy
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Hi, can someone please tell me what is wrong with this code? I just want it to check if the file size is greater than 2000kb.
if
Thanks!
---------- Post updated at 09:23 PM ---------- Previous update was at 09:21 PM ----------
I should probably post the full code:
#!/bin/sh... (9 Replies)
Discussion started by: Bengel
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6. UNIX for Dummies Questions & Answers
removed the link due to some issues and i got the information i needed (4 Replies)
Discussion started by: Amit Sura
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7. Shell Programming and Scripting
Hi All,
I am using Unix ksh script.
I need to insert values to a table using the o/p from a slelect statement.
Can anybody Help!
My script looks like tihs.
---`sqlplus -s username/password@SID << EOF
set heading off
set feedback off
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Discussion started by: nkosaraju
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In my ksh script, if the conditions of a if statement are true, then do nothing; otherwise, execute some commands.
How do I write the "do nothing" statement in the following example?
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if (( "$x"="1" && "$y"="a" && "$z"="happy" ))
then
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9. Programming
If I declare a structure as:
typedef struct
{
int id;
void* ptr;
int size;
} kpage_t;
And then use this to do some initialization...
*((kpage_t**)page->ptr) = page;
What exactly is being done? I have some trouble with pointers here... :(
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Discussion started by: Legend986
1 Replies
10. Shell Programming and Scripting
I am trying to set up a variable based on the name of the file.
function script_name {
if
then
job_name='MONITOR'
return job_name;
elsif
then
job_name='VERSION'
return job_name
fi
}
for i in `ls *log`
do
script_name $i
done. (4 Replies)
Discussion started by: oracle8
4 Replies
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)