Replace Stub Values In One Group Of Files With Actual Values From Another Group Of Files

UNIX for Beginners Q & A
1

I have two directories of files (new-config-files and old-config-files):

new-config-files/this-db/config.inc.php
new-config-files/that-db/config.inc.php
new-config-files/old-db/config.inc.php
new-config-files/new-db/config.inc.php
new-config-files/random-database/config.inc.php
etc.

old-config-files/this-db/config.inc.php
old-config-files/that-db/config.inc.php
old-config-files/old-db/config.inc.php
old-config-files/new-db/config.inc.php
old-config-files/random-database/config.inc.php
etc.

Example snippet of old file:

$cfg['Servers'][$i]['user'] = 'test-user';
$cfg['Servers'][$i]['password'] = 'test-user-password';
$cfg['Servers'][$i]['only_db'] = 'test-data';

Example snippet of new file:

$cfg['Servers'][$i]['user'] = 'DB-USER';
$cfg['Servers'][$i]['password'] = 'DB-PASSWORD';
$cfg['Servers'][$i]['only_db'] = 'DB-DATABASES';

I'd like to replace only the stub values (i.e., DB-USER, DB-PASSWORD, DB-DATABASES) in the new config files with the corresponding actual values (i.e., test-user, test-user-password, test-data) from the old config files.

It might also be good to know how to do this when there are no stub values, but only different values that should be replaced.

2 
for i in new-config-files/*/*                  # for list of files under new directory/subdirectory
do
   [[ -f ${i/new/old} ]] && {                                     # if same file name exists under new and old directories
      awk -F\' '                                                           # use awk with ' as field delimeter
      NR==FNR {val[$4]=$6; next}                       #  for first file read (old) store field 6 in var array stub key name (field 4)
      length(val[$4]) {$6=val[$4]}                        #  for second file read replace field 6 stored for the stub name if it exists
      1                                                                          # print line
      ' ${i/new/old} OFS=\' $i > $i.tmp                  # open old file new file (with ' as delimiter) redirect output to file with tmp extension
      mv -f $i.tmp $i                                                # move tmp extension file name to original file name (clobbers file)
   }
done

                                                    \# end loop

note: make a couple of test directories to test.

1 Like
3

This seems to work great, thank you!

Can you explain how it's working?

4

Thanks for the comments. I'm not understanding how the field 4 & 6 numbers are working -- how are these counted?

Assuming I have other lines in these files, will this replace those values too, or only where I have the stub values?
I'd like to only replace the stub values in this case. The old files may have lines that also exist in the new files, whose values I don't want to transpose. It seems to only have replaced the stub values ... how?

5

The field divider is a single quote ('). So field 4 is the stub name. To control which stubs to update, try using a control string. ex.:

update_stubs="user:password"

for i in new-config-files/*/*
do
   [[ -f ${i/new/old} ]] && {
      awk -F\' -v stubs="$update_stubs" '
      BEGIN {
         c=split(stubs, t_array, ":");
         for (i=1; i<=c; i++) update_stubs[t_array]=t_array;
      }
      NR==FNR {if (length(update_stubs[$4])) val[$4]=$6; next;}
      length(val[$4]) {$6=val[$4];}
      1
      ' ${i/new/old} OFS=\' $i > $i.tmp
      mv -f $i.tmp $i
   }
done