Java exec grep | linux fails

Question

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Ok, this one is tricky:

I call this command from Java with Process.exec():

grep -ne 'xxx\|yyy' file

and it only returns xxx?

Edit: I escape the \ with \\ in java.

But when I call the exact same command from the commandline on the same machine it returns both xxx and yyy as expected!?

I have tried everything, escaping more and less with -E, changing ' to " (which actually oddly doesn't work when you run from java either)?!

Has someone run in to the exact same odd problem?

Can you try this command: grep -ne 'xxx\\|yyy' file OR grep -n -e 'xxx' -e 'yyy' file ? — anubhava
– anubhava, Commented Mar 20, 2013 at 19:50
Of course I escape the \ in the java code with \\ othervise this wouldn't work at all. — user951335
– user951335, Commented Mar 20, 2013 at 19:59
If the | has to be escaped on the command line, you might have to use 3 or 4 \ characters in your Java string! — jahroy
– jahroy, Commented Mar 20, 2013 at 20:06
ok SOLVED thanks to anubhava... grep -n -e 'xxx' -e 'yyy' file didnt work but then I tried grep -n -e 'xxx' file and that didnt work either so I tried grep -ne 'xxx\|yyy\|zzz' file and THEN xxx and yyy returned lol — user951335
– user951335, Commented Mar 20, 2013 at 20:14

VishalDevgire · Accepted Answer · 2013-03-20 19:58:05Z

1

You will have to escape '\' by putting '\\' as follows :

.exec("grep -ne 'xxx\\|yyy' file");

edited Mar 20, 2013 at 19:58

answered Mar 20, 2013 at 19:51

VishalDevgire

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Jamie · Accepted Answer · 2013-03-20 20:07:45Z

1

This might be a dumb question, but why not use BufferedReader/readLine, and then String.indexOf or other regex, rather than shelling out to grep?

Grep is probably faster than Java at searching the file, but on the other hand, creating a child process from Java would probably negate any benefit gained there.

answered Mar 20, 2013 at 20:07

Jamie

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1 Comment

user951335 Over a year ago

Because xxx and yyy are complex and need regexp anyhow + the file is BIG!

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