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# 1  
Old 04-21-2011
grep command help
Hi guys,
I am trying to "grep" a line from the file which has a certain value (49 in my example below) from the begining of the line ONLY. I am using the following command:
Code:
$ PNUM=49
$ grep "^ *${PNUM} *" firmexbytes.dta
  494   8134     A023     A024
   49   812A     9871     9872
  492   A961     A962     A963
  491   0B77     0B78     0B79
  495   0B7A     0B7B     0B7C
$

The problem is that the above command returns more then I need.
May be someone knows the way to use "grep" in such a way that it returns only ONE line which contains the specified value (strict) if it is in the first colomn only. Thanks
# 2  
Old 04-21-2011
Code:
grep -E "^[ \t]*49[ \t]+" infile
   49   812A     9871     9872

# 3  
Old 04-21-2011
Thanks, but it seems that my shell has restrictions on -E option:
Code:
$ grep -E "^[ \t]*49[ \t]+" firmexbytes.dta
grep: illegal option -- E
Usage: grep -hblcnsviw pattern file . . .
$

Is there any walk around ? Thanks
# 4  
Old 04-21-2011
Quote:
Originally Posted by aoussenko
The problem is that the above command returns more then I need.
That's because '<space>*' searches for zero or more occurrences of a space. You need '<space><space>*', i.e. two spaces and an asterisk, to say I want at least one space:
Code:
$ grep "^ *${PNUM} *" firmexbytes.dta
  494   8134     A023     A024
   49   812A     9871     9872
  492   A961     A962     A963
  491   0B77     0B78     0B79
  495   0B7A     0B7B     0B7C
$ grep "^ *${PNUM}  *" firmexbytes.dta
   49   812A     9871     9872

You could also use awk to achieve the same goal:
Code:
$ awk -v pnum=49 '$1==pnum' firmexbytes.dta
   49   812A     9871     9872

Best regards,
Mark.
# 5  
Old 04-21-2011
Code:
awk '$1==49' file

This User Gave Thanks to Franklin52 For This Post:
rwuerth
# 6  
Old 04-21-2011
To keep it a bit more generic and yes, egrep or grep -E is not really needed, you can try this:

Code:
grep "^ *${PNUM} \+" infile
   49   812A     9871     9872

If there is just blanks it will work - if there is also tabs in between, it will not. You can either try for egrep or just use the solution Franklin posted.
# 7  
Old 04-21-2011
Thanks a lot to all you guys!
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