Visit Our UNIX and Linux User Community


Shift Question (Perl)


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Shift Question (Perl)
# 1  
Old 01-06-2009
Shift Question (Perl)

I am attempting to write a script that reads each line of a file into a separate array and does some work on it then puts it all back together and I think I need to use the 'shift()' command to read each line into its own array, but I need help nesting it into a while loop (while not eof)

So here is some of the raw data in the file:

Code:
Vallejo-1991-Jan-20-The_Bride-BLH
Vallejo-1991-Jan-20-The_Bride-BLH
Berkeley-1992-Jan-26-I_Corinth_14-BLH
berkeley-1992-Jan-26-I_Corinth_14-BLH
Union City-1991-July-14-Promises_covenent_of_circumcision-BLH
UC-1991-July-14-Promises_covenent_of_circumcision-BLH

I want the output to replace the Location (Vallejo, etc.) with a consistent syntax (Capital first letter and city spelled out; e.g. Union City, Vallejo, Berkeley, there are only these three locations) AND, more importantly I want to change the Month element into a number (e.g July - 07, Jan -01, unfortunately the abbreviations aren't always consistent, BUT the first three letters usually are (Jul, Jan, Aug, etc.)

So the output of the data above should be:

Vallejo-1991-01-20-The_Bride-BLH
Vallejo-1991-01-20-The_Bride-BLH
Berkeley-1992-01-26-I_Corinth_14-BLH
Berkeley-1992-01-26-I_Corinth_14-BLH
Union City-1991-07-14-Promises_covenent_of_circumcision-BLH
Union City-1991-07-14-Promises_covenent_of_circumcision-BLH

here is what I have so far:
Code:
# Open File containing raw data
open(FILE, "test2.txt") or die("unable to open file");

# read file into an array
@RawData = <FILE>;
close(FILE);
while (<>) {

#read in Folder name
@FileNames = shift(@RawData);

I know how to write the code to split the data into arrays BUT I dont know how to analyze and replace the data...
# 2  
Old 01-07-2009
You are somehow trying to read the same file twice. This line reads the ENTIRE file into the @RawData array:
Code:
@RawData = <FILE>;

Then you try to start reading from files listed on the command line (or standard input) with
Code:
while (<>) {

1. Maybe you mean:
Code:
open(FILE, "test2.txt") or die("...");
while (<FILE>) { 
   # process one line in $_ at a time...
}

I think that's what you want.

2. To process: use split()
Code:
# inside while loop
($city,$year,$month,$day,$title,$speaker)=split('-'); 

# Convert month name to a number, or print existing value if not found in mapping.
$month=exists $month2int{$month} ? $month2int{$month} : $month;

# Canonicalize city name: use the value found in the map; if not in the map, just capitalize first letter. 
$city=exists $citymap{$city} ? $citymap{$city} : ucfirst($city);

# reconstruct and print out line.
print join("-",$city,$year,$month,$day,$title,$speaker);

3. Define your "mappings" for month names and cities. Do this before the while loop. Fill in the ellipses with the rest of the information you'll need....
Code:
%citymap = ( UC => "Union City", VJ => "Vallejo", ... );
%month2int  = ( Jan => 1, Feb => 2, ...., Jul => 7, July => 7, ... Okt => 10, Oct => 10, October => 10, ... );

# 3  
Old 01-07-2009
Or maybe you mean:
Code:
@RawData = <FILE>
while ($_ = shift @RawData) {
...
}
## @RawData is empty

But in that case, it's simpler, better, and faster to use:
Code:
@RawData = <FILE>
foreach (@RawData) {
 ...
}
## @RawData contains processed data.

# 4  
Old 01-07-2009
help

Okay I'm getting a syntax error here is my code

Code:
open(FILE, "test2.txt") or die ("The file is not found");

$citymap = ( UC => "Union City", VJ => "Vallejo", Vallejo => "Vallejo", Union Ci
ty => "Union City", berk => "Berkeley", Berk => "Berkeley" );
$month2int  = ( Jan => 1, Feb => 2, Mar => 3, mar => 3, March => 3, Apr => 4, ap
r => 4, April => 4, may => 5, May => 5, Jun => 6, Jul => 7, July => 7, jul => 7,
 aug => 8, Aug => 8, August => 8, august => 8, Sept => 9, September => 9, sept =
> 9,Okt => 10, Oct => 10, October => 10, oct => 10, nov => 11, Nov => 11, Novemb
er => 11, november => 11, Dec => 12, December => 12, december => 12);

while (<FILE>) {
($city,$year,$month,$day,$title,$speaker)=split('-');
$month=exists $month2int{$month} ? $month2int{$month} : $month;
$city=exists $citymap{$city} ? $citymap{$city} : ucfirst($city);
print join("-",$city,$year,$month,$day,$title,$speaker);
}

I run the command:
Code:
perl ConvertingFileNames

and my error is:

Code:
syntax error at ConvertingFileNames line 3, near "Union City"
Execution of ConvertingFileNames aborted due to compilation errors.

I noticed in the code you gave me you had a prefix of "%" instead of "$" for the variables defining the month and Location...I tried running with both and it gives me the same error

So I like to talk my code out in words correct me if I'm wrong here but this is what I have so far:

1. Open the file with the file names
2. Define variables to compare the file to
3. While not eof take each line of the file and split it by "-" and put each split value into a unique variable
4. Check two of the variables (month and location) against the two variables defined before the "while" statement
5. make the appropriate changes or do nothing if nothing matches
6. print each line of the file back in the same order it was found with the appropriate changes
7. Close file

Can you help me with syntax?
# 5  
Old 01-08-2009
The problem is where you have:
Code:
Union City => "Union City",

The space is throwing off perl. But you DONT NEED to map every city name... if it's not in the hash array, the script will simply capitalize the first letter and take the rest. So:
Code:
berkeley => 'Berkeley', Vallejo => 'Vallejo'

are also not needed. However this IS needed (just in case):
Code:
"union city" => "Union City"

Otherwise you will get "Union city".
# 6  
Old 01-08-2009
Okay I got the script working...Thank you VERY much for your help...one more thing though
it minor dont worry...

I want the output to be as follows

YEAR-MN-DY-YR- Subject -BLH
so there should be a space before and after the subject
also I need the Month to be two digits
I tried altering the code by putting Feb => 02 instead of Feb => 2 but it errors out
I also tried changing the print line to ...,0$month,...or ...,'0' month,... that errors out as well

can you give me some guidance on syntax

#!/usr/bin/perl

open(FILE, "test3.txt") or die ("The file is not found");

%citymap = ( UC => "Union City", VJ => "Vallejo", Vallejo => "Vallejo",berk => "
Berkeley", Berk => "Berkeley" );
%month2int = ( Jan => 1, Feb => 2, Mar => 3, mar => 3, March => 3, Apr => 4, ap
r => 4, April => 4, may => 5, May => 5, Jun => 6, Jul => 7, July => 7, jul => 7,
aug => 8, Aug => 8, August => 8, august => 8, Sept => 9, September => 9, sept =
> 9,Okt => 10, Oct => 10, October => 10, oct => 10, nov => 11, Nov => 11, Novemb
er => 11, november => 11, Dec => 12, December => 12, december => 12);

while (<FILE>) {
($city,$year,$month,$day,$title,$speaker)=split('-');
$month=exists $month2int{$month} ? $month2int{$month} : $month;
$city=exists $citymap{$city} ? $citymap{$city} : ucfirst($city);
print join("- ",$city,$year,$month,$day,$title,$speaker);
# 7  
Old 01-08-2009
nvrmind...I just discovered "printf" :-) :-)

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Shift command help

#!/bin/bash hostname=$1; shift for hostname in $1 do ping $hostname done I want to run the above script as hostname.sh yahoo.com google.com cnn.com. I want to shift each hostname to $1. How can do that with above code as currently it's not shifting. (5 Replies)
Discussion started by: scj2012
5 Replies

2. Homework & Coursework Questions

Need help with a Perl Script using Pop, Shift, & Push

Hello everyone, I am new to Perl and I am having some issues getting a script to work. I have to create a script that uses an array of 52 cards, "shuffles" the cards (using loops with the pop, shift, and push commands), and prints out the top five. This is not a randomizing of the array just a... (2 Replies)
Discussion started by: Hax0rc1ph3r
2 Replies

3. Shell Programming and Scripting

Use of Shift command

Hello Expert Can any one please explain what is the use of shift command in general terms: set -- $(ls -t) shift rm -Rf $* what is the use of shift command over here. Thanks a lot for your help (2 Replies)
Discussion started by: aks_1902
2 Replies

4. UNIX for Dummies Questions & Answers

A Shift into UNIX

Hi, Firstly, I did a search for this question both on this site and on the internet and have not been able to find a suitable answer that is not general in nature. I have always been a Windows user. I use my girl friend's mac every now and then, but I always come back to windows. For a... (1 Reply)
Discussion started by: mearex
1 Replies

5. Shell Programming and Scripting

script assistance with shift J

Hey all, I need some assistance. I'm writing a script to eject tapes from a tape library, but the library is not a queued system and can only eject 15 tapes at a time. I added paste -d : -s so that it goes through full_tapes and puts each media_id on one line separated by the :. Now I'm... (2 Replies)
Discussion started by: em23
2 Replies

6. UNIX for Dummies Questions & Answers

shift not working

Hi, I wrote one script, in between script needs to use 10th and 11th positional parameters, that time i used "shift". Here i am facing the below find problem, ./DataCount.sh: cannot shift I tried 1) I have read man pages for shift 2) Before but * and ** 3) Simple shift with out giving... (4 Replies)
Discussion started by: Nagapandi
4 Replies

7. Shell Programming and Scripting

shift and push question in perl

hi, another perl question, I don't understand the below while (<FILE>) { push @last5, $_; #add to the end shift @last5 if @last5 > 5 ; #take from the beginning } can someone please explain to me how does shift @last5 if @last5 > 5 is taking last 5 lines from... (5 Replies)
Discussion started by: hankooknara
5 Replies

8. Shell Programming and Scripting

Regarding the shift command???

I am running a program where in I have this command which is giving error the shift: number is not correct. can you please tell me how shift actually works? the line which is giving error is- set $PARAM; shift; shift; shift; shift; shift; shift; shift; shift Is it related somewhere to... (2 Replies)
Discussion started by: shrao
2 Replies

9. Shell Programming and Scripting

shift command

Hi Folks, In shell scripting the maximum no. of command line parameters becomes 9(Am i right). If we want to get more than 9 parameters we use the shift command. Even here there are two possibilities. 1. Without the use of variables - The arguments are lost and the lost no. is equal to the... (6 Replies)
Discussion started by: Nisha
6 Replies

10. UNIX for Dummies Questions & Answers

shift command

There is an error when i am trying to use the shift command in this way: ($1 = -d, $2 = 123, $3 = -c etc etc) for $arg in $@ do case $arg in "-d") shift; (so that the $2 will become the $arg now) (and while it loop the 2nd time,) ... (1 Reply)
Discussion started by: AkumaTay
1 Replies

Featured Tech Videos