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Top Forums Shell Programming and Scripting Using awk to read one file and search in another file Post 302735939 by pchang on Monday 26th of November 2012 11:44:37 AM
Old 11-26-2012
Quote:
Originally Posted by Klashxx
Try this (and donīt forget the code tags in your posts):
Code:
awk -F\| 'NR==FNR{a[$1]++;next}a[$1]'  file1 file2

Wow - it's blazing FAST!!!!

Done within seconds.

Can you explain the code a little bit?

I can understand that file1 is being stored in an array but I cannot understand the rest.

Thanks.

---------- Post updated at 11:44 AM ---------- Previous update was at 11:43 AM ----------

Quote:
Originally Posted by RudiC
PLEASE use code tags.

A small modifation to your own code will make it do what you expect:
Code:
awk -F"|" '
           FNR==NR {f1[$1];next}
           ($1 in f1)
          ' file1 file2

, but I don't think it will be much faster than grep. Pls report back the time differences!
Not even comparable - fgrep was very slow but awk came back within seconds.
 

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DIFF(1) 						      General Commands Manual							   DIFF(1)

NAME
diff - print differences between two files SYNOPSIS
diff [-c | -e | -C n] [-br]file1 file2 OPTIONS
-C n Produce output that contains n lines of context -b Ignore white space when comparing -c Produce output that contains three lines of context -e Produce an ed-script to convert file1 into file2 -r Apply diff recursively to files and directories of EXAMPLES
diff file1 file2 # Print differences between 2 files diff -C 0 file1 file2 # Same as above diff -C 3 file1 file2 # Output three lines of context with every diff -c file1 file2 # Same diff /etc /dev # Compares recursively the directories /etc and /dev diff passwd /etc # Compares ./passwd to /etc/passwd DESCRIPTION
the same name, when file1 and file2 are both directories" difference encountered" Diff compares two files and generates a list of lines telling how the two files differ. Lines may not be longer than 128 characters. If the two arguments on the command line are both directories, diff recursively steps through all subdirectories comparing files of the same name. If a file name is found only in one directory, a diagnostic message is written to stdout. A file that is of either block special, character special or FIFO special type, cannot be compared to any other file. On the other hand, if there is one directory and one file given on the command line, diff tries to compare the file with the same name as file in the directory directory. SEE ALSO
cdiff(1), cmp(1), comm(1), patch(1). DIFF(1)
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