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Full Discussion: grep -v -f xxxxxxx
Top Forums Shell Programming and Scripting grep -v -f xxxxxxx Post 12030 by peter.herlihy on Monday 17th of December 2001 05:48:36 PM
Old 12-17-2001
Network grep -v -f xxxxxxx

I've got the code below. It does it's job but it's scrappy. Can someone explain why grep -v -f doesn't work against an empty file?

Basically I have a file of presumed good data - I want to remove any by comparing with a file I know are bad. When the bad file is empty - the output file is also empty. It's weird.

Works fine when the bad file has some data - so you'll see the cheap hack fix I've put in.


if [ -s tmp.merge.nos ]
then
join -t, -v 1 tmp.both tmp.req.merges | sed 's/=/,/' | grep -v -f tmp.merge.nos > $infile.ready
else
join -t, -v 1 tmp.both tmp.req.merges | sed 's/=/,/' > $infile.ready
fi

Maybe comm would be better - but I'd like to know why it doesn't work anyway (grep -v -f). CheersSmilie
 

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cdbmake(1)						      General Commands Manual							cdbmake(1)

NAME
cdbmake - create a constant database SYNOPSIS
cdbmake cdb cdb.tmp DESCRIPTION
cdbmake reads a series of encoded records from its standard input and writes a constant database to cdb. cdbmake ensures that cdb is updated atomically, so programs reading cdb never have to wait for cdbmake to finish. It does this by first writing the database to cdb.tmp and then moving cdb.tmp on top of cdb. If cdb.tmp already exists, it is destroyed. The directories con- taining cdb.tmp and cdb must be writable to cdbmake; they must also be on the same filesystem. cdbmake always makes sure that cdb.tmp is safely written to disk before it replaces cdb. If the input is in a bad format or if cdbmake has any trouble writing cdb.tmp to disk, cdbmake complains and leaves cdb alone. RECORD FORMAT Records are indexed by keys. A key is a string. cdb is structured so that another program, starting from a key, can quickly find the rel- evant record. cdbmake allows several records with the same key, although most readers take only the first record, and cdbmake slows down somewhat if there are many records with the same key. cdbmake and cdbdump(1) preserve the order of records. A record is encoded for cdbmake as +klen,dlen:key->data followed by a newline. Here klen is the number of bytes in key and dlen is the number of bytes in data. The end of data is indicated by an extra newline. For example: +3,5:one->Hello +3,7:two->Goodbye key and data may contain any characters, including colons, dashes, newlines, and nulls. Keys and data do not have to fit into memory. A database cannot exceed 4 gigabytes. cdb is portable across machines. SEE ALSO
cdbdump(1), cdbget(1), cdbstats(1) cdbmake(1)
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