Using GREP to extract variable following a string

modey3 · #1 (**permalink**) 02-08-2009

Hello,

I'm running calculations and I need to extract a specific number from a output file. So far I've only been able to GREP entire lines containing the string: '1 F=' . I would like to go a step further and extract just the number following '1 F='. The entire line looks like:

1 F= -.13250138E+03 E0= -.13249556E+03 d E =-.174650E-01 mag= 35.2157

The number I would like to extract is in red. Thanks for any help.

modey3

Radar · #2 (**permalink**) 02-08-2009

Code:

[radar@msi-k8t:~]$ cat testfile.txt
1 F= -.13250138E+03 E0= -.13249556E+03 d E =-.174650E-01 mag= 35.2157
[radar@msi-k8t:~]$ grep "1 F=" testfile.txt | awk '{print $3}'
-.13250138E+03

vgersh99 · #3 (**permalink**) 02-08-2009

Quote:

Originally Posted by Radar

Code:

[radar@msi-k8t:~]$ cat testfile.txt
1 F= -.13250138E+03 E0= -.13249556E+03 d E =-.174650E-01 mag= 35.2157
[radar@msi-k8t:~]$ grep "1 F=" testfile.txt | awk '{print $3}'
-.13250138E+03

why exactly do you need 'grep'?

Radar · #4 (**permalink**) 02-08-2009

Quote:

Originally Posted by vgersh99

why exactly do you need 'grep'?

Because the file in question more than likely contains multiple lines, not all of which contain the needed pattern.

Annihilannic · #5 (**permalink**) 02-08-2009

I think vger's point is that awk can do that bit too:

Code:

awk '/1 F=/ { print $3 }' testfile.txt

vgersh99 · #6 (**permalink**) 02-09-2009

Quote:

Originally Posted by Annihilannic

I think vger's point is that awk can do that bit too:

Code:

awk '/1 F=/ { print $3 }' testfile.txt

Code:

awk '$1=="1" && $2 == "F=" { print $3 }' testfile.txt

Annihilannic · #7 (**permalink**) 02-09-2009

Quote:

Originally Posted by vgersh99

Code:

awk '$1=="1" && $2 == "1 F=" { print $3 }' testfile.txt

Is that better somehow vger? I think you meant $2 == "F=" in there...

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