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Chapter 33 Batch Editing |
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Chapter 33 Batch Editing |
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Q: My Bourne shell script ( 44.1 ) calls ed to edit a set of files:
Q:
= for << \ |
site=something cmty=somethingelse for i in file1 file2 file3 do ed $i << end 1,\$s/pat1/$site/g 1,\$s/pat2/$cmty/g w q end done |
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Q: It works fine except when one of the files does not contain pat1 . ed doesn't update that file, even though it could have matched pat2 . The other files are edited as they should be.
A:
On an error - including "no matches" -
ed
attempts to discard any unread commands. If you are running
ed
"by hand" this has no effect, but if its input is from a file, this makes EOF -d-of-file) the next thing it sees. You could remove the
q
command and you would see the same behavior, as
ed
automatically quits at end-of-file.
There is a simple workaround. Unlike the
s
command, the
global
command
g
does not report an error if no lines match. Thus:
ed - $i << end g/pat1/s//$site/g g/pat2/s//$cmty/g w end
The
-
(dash) flag suppresses the two numbers that
ed
normally prints when reading and writing files. These are the number of characters in the file, and are usually irrelevant. [As Chris explained, the
q
in the original script isn't needed.
-JP
]
- in comp.unix.questions on Usenet, 16 May 1989
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| 33.6 Change Many Files by Editing Just One |
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33.8 Batch Editing Gotcha: Editors Bomb on Big Files |
