The unix utility join will do this (assuming that file1 and file2 are sorted): 
    $ join -t\| file1 file2

    A1|dog||Fido|
    A2|cat||Fluffy|
    A3|bird||Tweety|

[download]
From which you could filter out the extra empty field or extend the command line options to select specific fields: 
    $ join -t\| -o 1.1 1.2 2.2 2.3 file1 file2

    A1|dog|Fido|
    A2|cat|Fluffy|
    A3|bird|Tweety|

[download]

--
John.

In reply to Re: combining 2 files with a comon field by jmcnamara
in thread combining 2 files with a comon field by jjohhn

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