10-12-2003
Perl: sorting files by whats in'em
i'm halfway into my script and realize i may need to use an associative array (a hash, i guess they are called in Perl). i'm fairly new to Perl and don't know how to use them correctly.
i have some files in a directory. each file contains a number in a specific place in it's header. what i would like to do is create a list of the files in a text file that has them sorted according to this number. there is also one other thing. some of the files' numbers "overlap" and i don't want these files included. since this is kind of weird to explain i'll use the following example:
below is the list of files along with their associated numbers before they are sorted. notice at "file12" the numbers start overlapping and starting with "file21" the numbers reach the point past -0.5 (which is file11's number). i basically do not want files 12 through 20 included in my text file.
"file1",-30.5
"file2",-27.5
"file3",-24.5
"file4",-21.5
"file5",-18.5
"file6",-15.5
"file7",-12.5
"file8",-9.5
"file9",-6.5
"file10",-3.5
"file11",-0.5
"file12",-26.5
"file13",-23.5
"file14",-20.5
"file15",-17.5
"file16",-14.5
"file17",-11.5
"file18",-8.5
"file19",-5.5
"file20",-2.5
"file21",0.5
"file22",3.5
"file23",6.5
"file24",9.5
"file25",12.5
"file26",15.5
"file27",18.5
"file28",21.5
"file29",24.5
"file30",27.5
"file31",30.5
here is the way the text file with the sorting should look:
"file1",-30.5
"file2",-27.5
"file3",-24.5
"file4",-21.5
"file5",-18.5
"file6",-15.5
"file7",-12.5
"file8",-9.5
"file9",-6.5
"file10",-3.5
"file11",-0.5
"file21",0.5
"file22",3.5
"file23",6.5
"file24",9.5
"file25",12.5
"file26",15.5
"file27",18.5
"file28",21.5
"file29",24.5
"file30",27.5
"file31",30.5
Note: the quotes aren't part of the file names and the file names for the files are not named so that you can "deduce" the order (file1 -> file31), they are for all intents and purposes random. Also, i know the numbers increase by 3 (and that is how they increase), but the gap in between the cut off is only 1 (from -0.5 to 0.5), and this is ok. i basically cannot have a gap more than 3.
what i'm thinking is that an associative array may be appropriate, but i'm not sure. my logic so far has been to first, find the smallest number and write it's corresponding filename to the text file. then find the filename with the first file's number + 3, and append that filename to the textfile. then, if no more files fit that criteria, start appending the filenames by which is larger than the last one. i think this would work but i don't know how to do it.
thanks in advance for helping. this will save me lots of time, since i have many directories like this and sorting them by hand takes a long time.
10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
Because I am not creative, I did this:
find . -type f -name '*.GIF'|cut -d'/' -f2|awk -F. '{print "mv "$1".GIF "$1".gif --reply=yes"}' > case.sh
Then ran the case.sh - I was wondering if you guys could come up with something more efficient? Or even limit CPU useage? It is killing my poor ext3... (3 Replies)
Discussion started by: r0sc0
3 Replies
2. Shell Programming and Scripting
I have many files that I need to sort each week. I know how to do in Unix, but for this task it appears best to do native inside an existing perl program. So, simplified, I have a file similar to the following:
Joe_________12_Main_St__A001________LX
Benny_______5_Spring____A002________LX... (5 Replies)
Discussion started by: joeyg
5 Replies
3. Shell Programming and Scripting
Hello,
I have a page where multiple fields and their values are displayed. But I am able to sort only a few fields. When I looked into the issue, it is seen that the for each row of info , an unique id is generated and id.txt is generated and saved. Only those fields which are inside that id.txt... (3 Replies)
Discussion started by: eagercyber
3 Replies
4. Shell Programming and Scripting
E:\>perl -00ne 'push @a,"$_\0$ARGV\n";END{print reverse split/\0/ for sort @a}' file1-obj_prof.out.txt file2-obj_prof.out.txt'
Can't find string terminator "'" anywhere before EOF at -e line 1. (6 Replies)
Discussion started by: richsark
6 Replies
5. Shell Programming and Scripting
Hi,
I have a file in this format:
a b c d e
a b c d e
a b c d e
i need perl script to sort 2nd column in alphabatical order
The script i use is
#!/usr/bin/perl
my @words=<>;
foreach(sort mysort @words) {
print; (4 Replies)
Discussion started by: Learnerabc
4 Replies
6. Shell Programming and Scripting
Good morning!!
Im trying to practice withe Perl and sorting variables is not going good at all!
#!/usr/bin/perl
$username = $ENV {'LOGNAME'};
print "Hello, $username\n";
I want to add sort and 'mail' and 'home'. This below is what I have came up with,but of course its not working.
... (5 Replies)
Discussion started by: bigben1220
5 Replies
7. Shell Programming and Scripting
I have a file abc.txt which contains data in th following format
abc,23
hgfh,87
tweg,89
jdfjn,74
I want to sort on the basis of column (the second one). It should be numerical sort.
output should be
abc,23
jdfjn,74
hgfh,87
tweg,89
I know how to do it in unix. I need a PERL code (1 Reply)
Discussion started by: centurion_13
1 Replies
8. Shell Programming and Scripting
Hi all,
Not sure if this should be in the programming forum, but I believe it will get more response under the Shell Programming and Scripting FORUM.
Am trying to write a customized df script in Perl and need some help with regards to using arrays and file handlers.
At the moment am... (3 Replies)
Discussion started by: newbie_01
3 Replies
9. Shell Programming and Scripting
I have a directory of backup files.
named like this:
ldap.data.04-06-2012.tar
ldap.data.03-06-2012.tar
ldap.data.02-06-2012.tar
ldap.data.01-06-2012.tar
ldap.data.31-05-2012.tar
ldap.data.30-05-2012.tar
ldap.data.29-05-2012.tar
ldap.data.28-05-2012.tar
ldap.data.27-05-2012.tar... (6 Replies)
Discussion started by: robsonde
6 Replies
10. Shell Programming and Scripting
Hey guys,
I have started to learn perl recently because of a position I took. They want me to master perl and I've been reading books and practicing myself.
Basically I,m having my perl script run through a text pad and give the output in a special way
e.g
input
deviceconfig {
... (5 Replies)
Discussion started by: zee3b
5 Replies
A2P(1) Perl Programmers Reference Guide A2P(1)
NAME
a2p - Awk to Perl translator
SYNOPSIS
a2p [options] [filename]
DESCRIPTION
A2p takes an awk script specified on the command line (or from standard input) and produces a comparable perl script on the standard
output.
OPTIONS
Options include:
-D<number>
sets debugging flags.
-F<character>
tells a2p that this awk script is always invoked with this -F switch.
-n<fieldlist>
specifies the names of the input fields if input does not have to be split into an array. If you were translating an awk script that
processes the password file, you might say:
a2p -7 -nlogin.password.uid.gid.gcos.shell.home
Any delimiter can be used to separate the field names.
-<number>
causes a2p to assume that input will always have that many fields.
-o tells a2p to use old awk behavior. The only current differences are:
o Old awk always has a line loop, even if there are no line actions, whereas new awk does not.
o In old awk, sprintf is extremely greedy about its arguments. For example, given the statement
print sprintf(some_args), extra_args;
old awk considers extra_args to be arguments to "sprintf"; new awk considers them arguments to "print".
"Considerations"
A2p cannot do as good a job translating as a human would, but it usually does pretty well. There are some areas where you may want to
examine the perl script produced and tweak it some. Here are some of them, in no particular order.
There is an awk idiom of putting int() around a string expression to force numeric interpretation, even though the argument is always
integer anyway. This is generally unneeded in perl, but a2p can't tell if the argument is always going to be integer, so it leaves it in.
You may wish to remove it.
Perl differentiates numeric comparison from string comparison. Awk has one operator for both that decides at run time which comparison to
do. A2p does not try to do a complete job of awk emulation at this point. Instead it guesses which one you want. It's almost always
right, but it can be spoofed. All such guesses are marked with the comment ""#???"". You should go through and check them. You might
want to run at least once with the -w switch to perl, which will warn you if you use == where you should have used eq.
Perl does not attempt to emulate the behavior of awk in which nonexistent array elements spring into existence simply by being referenced.
If somehow you are relying on this mechanism to create null entries for a subsequent for...in, they won't be there in perl.
If a2p makes a split line that assigns to a list of variables that looks like (Fld1, Fld2, Fld3...) you may want to rerun a2p using the -n
option mentioned above. This will let you name the fields throughout the script. If it splits to an array instead, the script is probably
referring to the number of fields somewhere.
The exit statement in awk doesn't necessarily exit; it goes to the END block if there is one. Awk scripts that do contortions within the
END block to bypass the block under such circumstances can be simplified by removing the conditional in the END block and just exiting
directly from the perl script.
Perl has two kinds of array, numerically-indexed and associative. Perl associative arrays are called "hashes". Awk arrays are usually
translated to hashes, but if you happen to know that the index is always going to be numeric you could change the {...} to [...].
Iteration over a hash is done using the keys() function, but iteration over an array is NOT. You might need to modify any loop that
iterates over such an array.
Awk starts by assuming OFMT has the value %.6g. Perl starts by assuming its equivalent, $#, to have the value %.20g. You'll want to set
$# explicitly if you use the default value of OFMT.
Near the top of the line loop will be the split operation that is implicit in the awk script. There are times when you can move this down
past some conditionals that test the entire record so that the split is not done as often.
For aesthetic reasons you may wish to change index variables from being 1-based (awk style) to 0-based (Perl style). Be sure to change all
operations the variable is involved in to match.
Cute comments that say "# Here is a workaround because awk is dumb" are passed through unmodified.
Awk scripts are often embedded in a shell script that pipes stuff into and out of awk. Often the shell script wrapper can be incorporated
into the perl script, since perl can start up pipes into and out of itself, and can do other things that awk can't do by itself.
Scripts that refer to the special variables RSTART and RLENGTH can often be simplified by referring to the variables $`, $& and $', as long
as they are within the scope of the pattern match that sets them.
The produced perl script may have subroutines defined to deal with awk's semantics regarding getline and print. Since a2p usually picks
correctness over efficiency. it is almost always possible to rewrite such code to be more efficient by discarding the semantic sugar.
For efficiency, you may wish to remove the keyword from any return statement that is the last statement executed in a subroutine. A2p
catches the most common case, but doesn't analyze embedded blocks for subtler cases.
ARGV[0] translates to $ARGV0, but ARGV[n] translates to $ARGV[$n-1]. A loop that tries to iterate over ARGV[0] won't find it.
ENVIRONMENT
A2p uses no environment variables.
AUTHOR
Larry Wall <larry@wall.org>
FILES
SEE ALSO
perl The perl compiler/interpreter
s2p sed to perl translator
DIAGNOSTICS
BUGS
It would be possible to emulate awk's behavior in selecting string versus numeric operations at run time by inspection of the operands, but
it would be gross and inefficient. Besides, a2p almost always guesses right.
Storage for the awk syntax tree is currently static, and can run out.
perl v5.16.2 2012-08-26 A2P(1)