Assigning values to 2 variables within for loop

Shell Programming and Scripting
1

Hi All,

Is it possible to grep for two files and assign their names to two separate variables with for loop? I am doing the below currently:

if [ $FLAG = 0 ]
   then
        for fname in $( cd $dirA ; ls -tr | grep "^Ucountry_file$")
        do
              InFile=$dirA/$fname
              OutFile=$dirB/$fname.processed
                        :
                        :
                        :
               more lines of code
        done
fi

fname in the for loop here holds the name of the Ucountry_file. Likewise, in the same $dirA, there is another file called Rcountry_file. I want to grep for that as well and assign to another variable using the same for loop. Can it be done?

Thanks in advance.

2

I think you want to use egrep to extend the grep capability. You could:-

.... egrep "^Ucountry_file$|^Rcountry_file$"
.... egrep "^[UR]country_file$"

Have I got this right, or have I missed the point?

The first option specifies the name you are after with a | to make it an 'or' comparison. The second option searches for a line starting with either U or R, following by country_file then the end of the line.

I hope that this helps, but let me know if I'm miles off track. I must admit I don't know where $dirB comes from in your code.

Robin
Liverpool/Blackburn
UK

4

In general, instead of cramming thousands of filenames in backticks into a for, you should be doing command | command | while read because for has some problems here, like a limit on number of files, and potential accidental splitting on spaces instead of lines.

Anyway. You can do two greps separately, saving one into a file, then opening the file to read later...

command1 > /tmp/$$

exec 5</tmp/$$ # Open file into FD 5
rm /tmp/$$ # Delete file (Will stay readable until you close it )

command2 | while read LINE1
do
        read LINE2 <&5

        echo "LINE1 $LINE1 LINE2 $LINE2"
done

exec 5<&- # Close file
1 Like
5

Why all that ls, cd, grep at all? Try

for InFile in "$dirA/[RU]country_file"; do OutFile="$InFile".processed;...;done
6

I must be missing something basic here. I'll go a small step beyond where RudiC went. I don't see the need for a for loop at all. If I'm reading the code correctly the commands in the for loop will be executed once if $dirA/Ucountry_file exists and will not be executed if that file does not exist. If I understand the question correctly, I think the following would be a much simpler way to handle it:

ft=country_file
fname=U$ft
if [ $FLAG = 0 ]
then
        if [ -e "$dirA/R$ft ] && [ -e "$dirA/$fname" ]
        then
                InFile=$dirA/$fname
                InFile2=$dirA/R$ft
                OutFile=$dirB/$fname.processed
                        :
                        :
                        :
                more lines of code
        else    ... do ... if Rcountry_file or Ucountry_file is missing ...
        fi
fi

In the then part of the inner if, $fname will be what it was in the original for loop, $InFile will be as it was in the original for loop (a pathname for the Ucountry_file in $dirA) and $InFile2 will be a pathname for the Rcountry_file in $dirA.

1 Like