why it deletes all the contents of the file when I add" > file" after sort? "sort -k2 file > file".If the name already exist then we dont add it. how should we do?Thank you!
If you're saying that only want to add the given name to your file (without checking to see whether or not that name was already in the file, AND you don't need the line where it was added, the way to do that would be:
and if you wanted to only add that name if it was not already in the file:
When you use the command line:
the shell sees the redirection (> file) and creates a file named file (destroying any contents that may have existed in that file) and then starts the sort utility. The sort utility will then open the file named as a command-line argument (in this case also named file which, after the shell has redirected the output, is now an empty file).
This User Gave Thanks to Don Cragun For This Post:
Hi,
I have a huge file & I want to add a specific text in column. But I want to add this text from a specific line number to a specific line number & another text in to another range of line numbers.
To be more specific: lets say my file has 1000 lines & 4 Columns. I want to add text "Hello"... (2 Replies)
Hi,
I am using below command to display the number of line, but its returning no of lines along with file name.
But i want only no of line in the variable p.
Please help me on this?
p=`wc -l "text file"`
echo "$p" (6 Replies)
I having file below o/p
ibapp311dg,,20480,s,,,,,,,,,
test,,20480,s,,,,,,,,,
test,,20480,s,,,,,,,,,
ibapp311dg,,20480,s,,,,,,,,,
I want to to chk unique word line in the first field seperated by , as well as addup corressponding the number in field for each unique word like
ibapp311dg... (8 Replies)
Hello
Wondering if anybody may be able to advise on how I can filter the contents of the following file:
<object_name>-<version> <Instance>
GM_GUI_code.fmb-4 1
GM_GUI_code.fmb-5 1
GM_GUI_code.fmx-4 ... (7 Replies)
Hello Everyone.
I am trying to display contains of a file from a specific line to a specific line(let say, from line number 3 to line number 5). For this I got the shell script as shown below:
if ; then
if ; then
tail +$1 $3 | head -n $2
else
... (5 Replies)
I have a text file that has data like:
Data "12345#22"
Fred
ID 12345
Age 45
Wilma
Dino
Data "123#22"
Tarzan
ID 123
Age 33
Jane
I need to figure out a way of adding 1,000,000 to the specific lines (always same format) in the file, so it becomes:
Data "1012345#22"
Fred
ID... (16 Replies)
Hi
I want to delete a line from a txt file for which the line number is user input. Say when user selects 19, the 19th line would be deleted from the file. Can anyone please provide me with a sed one liner for the same... I tried sed -i. The interaction would be like this
Enter the line to... (1 Reply)
Given a file like this:
abc
def
ghi
I need to get to
somestandardtext abc1 morestandardtext
somestandardtext def2 morestandardtext
somestandardtext ghi3 morestandardtext
Notice that in addition to the standard text there is the line number added in as well. What I conceived is... (4 Replies)
Hi all,
I have 20 files (file001.txt upto file020.txt) and I want to read them from 3rd line upto end of file (line 1002). But in the final file they should appear to start from line 1.
I need following kind of output in a single file:
Filename Line number 2ndcolumn 4thcolumn
I... (14 Replies)
Discussion started by: bioinfo
14 Replies
LEARN ABOUT REDHAT
sort
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 $current = sort::current(); # identify prevailing algorithm
DESCRIPTION
With the "sort" pragma you can control the behaviour of the builtin "sort()" function.
In Perl versions 5.6 and earlier the quicksort algorithm was used to implement "sort()", but in Perl 5.8 a mergesort algorithm was also
made available, mainly to guarantee worst case O(N log N) behaviour: the worst case of quicksort is O(N**2). In Perl 5.8 and later, quick-
sort defends against quadratic behaviour by shuffling large arrays before sorting.
A stable sort means that for records that compare equal, the original input ordering is preserved. Mergesort is stable, quicksort is not.
Stability will matter only if elements that compare equal can be distinguished in some other way. That means that simple numerical and
lexical sorts do not profit from stability, since equal elements are indistinguishable. However, with a comparison such as
{ substr($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 compli-
cated 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
This pragma is not lexically scoped: its effect is global to the program it appears in. That means the following will probably not do what
you expect, because both pragmas take effect at compile time, before either "sort()" happens.
{ use sort "_quicksort";
print sort::current . "
";
@a = sort @b;
}
{ use sort "stable";
print sort::current . "
";
@c = sort @d;
}
# prints:
# quicksort stable
# quicksort stable
You can achieve the effect you probably wanted by using "eval()" to defer the pragmas until run time. Use the quoted argument form of
"eval()", not the BLOCK form, as in
eval { use sort "_quicksort" }; # WRONG
or the effect will still be at compile time. Reset to default options before selecting other subpragmas (in case somebody carelessly left
them on) and after sorting, as a courtesy to others.
{ 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
}
# prints:
# quicksort
# stable
Scoping for this pragma may change in future versions.
perl v5.8.0 2002-06-01 sort(3pm)