language-agnostic

How to merge two files consistently line by line

I have two files (file1.txt & file2.txt ). The files are only examples.

How can I merge the two files, in order to create the file - merge_files.txt as example 3?

I am now writing a KornShell (ksh) script, so merge can be done with KornShell, AWK, sed, a Perl one-liner, etc.

Background - why I need to merge the files: my target is to rename the old file (exist in first field) to a new file (exist in the second field).

Example 1

File file1.txt

/etc/port1-192.9.200.1-255.555.255.0
/etc/port2-192.9.200.1-255.555.255.0
/etc/port3-192.9.200.1-255.555.255.0
/etc/port4-192.9.200.1-255.555.255.0
/etc/port5-192.9.200.1-255.555.255.0
.
.
.
.

Example 2

File file2.txt

/etc/port1-192.90.2.1-255.555.0.0
/etc/port2-192.90.2.1-255.555.0.0
/etc/port3-192.90.2.1-255.555.0.0
/etc/port4-192.90.2.1-255.555.0.0
/etc/port5-192.90.2.1-255.555.0.0
.
.
.
.

Example 3

File merge_files.txt

/etc/port1-192.9.200.1-255.555.255.0  /etc/port1-192.90.2.1-255.555.0.0
/etc/port2-192.9.200.1-255.555.255.0  /etc/port2-192.90.2.1-255.555.0.0
/etc/port3-192.9.200.1-255.555.255.0  /etc/port3-192.90.2.1-255.555.0.0
/etc/port4-192.9.200.1-255.555.255.0  /etc/port4-192.90.2.1-255.555.0.0
/etc/port5-192.9.200.1-255.555.255.0  /etc/port5-192.90.2.1-255.555.0.0
.
.
.
.
.

Example 4 (merge_files.txt structure)

first field                           second field

OLD file                              NEW file
Solution

  • You can use paste to format the files side by side:

    $ paste -d" " file1.txt file2.txt
/etc/port1-192.9.200.1-255.555.255.0 /etc/port1-192.90.2.1-255.555.0.0
/etc/port2-192.9.200.1-255.555.255.0 /etc/port2-192.90.2.1-255.555.0.0
/etc/port3-192.9.200.1-255.555.255.0 /etc/port3-192.90.2.1-255.555.0.0
/etc/port4-192.9.200.1-255.555.255.0 /etc/port4-192.90.2.1-255.555.0.0
/etc/port5-192.9.200.1-255.555.255.0 /etc/port5-192.90.2.1-255.555.0.0

    E.g.:

    $ paste -d" " file1.txt file2.txt | while read from to; do echo mv "${from}" "${to}"; done
mv /etc/port1-192.9.200.1-255.555.255.0 /etc/port1-192.90.2.1-255.555.0.0
mv /etc/port2-192.9.200.1-255.555.255.0 /etc/port2-192.90.2.1-255.555.0.0
mv /etc/port3-192.9.200.1-255.555.255.0 /etc/port3-192.90.2.1-255.555.0.0
mv /etc/port4-192.9.200.1-255.555.255.0 /etc/port4-192.90.2.1-255.555.0.0
mv /etc/port5-192.9.200.1-255.555.255.0 /etc/port5-192.90.2.1-255.555.0.0

    Of course you would want to throw in some safety checks ([ -f "${from}" ], ...).

    Disclaimer: Works only if there are no spaces in your filenames.