Expand Variables and Wildcards into another variable.

UNIX for Beginners Q & A
1

Dear Forum members,

I am having trouble getting the complete filename (and directory path) in a variable.

Output directory mentioned in the code have three files:

DISPLAY_CITY_DETAILS_15-05-2019-08-29-26_MIGRATE_london.out
DISPLAY_CITY_DETAILS_15-05-2019-08-29-26_MIGRATE_paris.out
DISPLAY_CITY_DETAILS_15-05-2019-08-29-26_MIGRATE_rome.out

******************************************************
Code is as shown below:
I am tryin to get get the full path of the above files (including directory path in variable file_path).



output_dir=$HOME'/country/city/'

while IFS= read -r city_name
do
    
 ## None of the below command  worked.    



     file_path=`${output_dir}/*MIGRATE*${city_name}*.out`
    # eval file_path=`${output_dir}/*MIGRATE*${city_name}*.out`
    # file_path=${eval echo `ls ${output_dir} | grep "MIGRATE"`}
    # eval file_path=`ls ${output_dir} | grep "MIGRATE"`
       
    echo $file_path
 
done < ${city_list}    

##  city_list is the list of cities for which I want to display details

Can anybody help with the command?

Thanks.

2 
file_path=${output_dir}
files_list=`ls ${output_dir}/*MIGRATE*${city_name}*.out`
1 Like
3

Thanks Anbu23 for quick reply. The command sent by you is working.

But what is the difference between below two?

file_path=${output_dir} 

files_list=`ls ${output_dir}/*MIGRATE*${city_name}*.out`

and

file_path=${output_dir} 

files_list=`echo ${output_dir}/*MIGRATE*${city_name}*.out`

both seems to be working..

4

A very, very simple example:

Last login: Wed May 15 18:04:12 on ttys000
AMIGA:amiga~> ls Au*
AudioScope.Circuits       AudioScope.sh
AudioScope.Config         AudioScope_1.sh
AudioScope.Manual         AudioScope_Quick_Start.Notes
AMIGA:amiga~> 
AMIGA:amiga~> echo Au*
AudioScope.Circuits AudioScope.Config AudioScope.Manual AudioScope.sh AudioScope_1.sh AudioScope_Quick_Start.Notes
AMIGA:amiga~> _
5

You see the difference with

echo "$file_path"

The quotes prevent the shell to do word-splitting on command arguments.

ls is an external command. The efficient per-line formatter is printf "%s\n" that 1. is a shell-builtin and 2. does no extra I/O.

What do you want to do with the $file_path?
It can make sense to not expand it too early. For example

file_path="${output_dir}/*MIGRATE*${city_name}*.out"
for f in $file_path

is smarter than

file_path=`ls ${output_dir}/*MIGRATE*${city_name}*.out`
for f in $file_path