Parse text file to retrieve values from BASH

eco_bach · 12-08-2016, 03:49 PM

Lets say I have a file file_list.txt

This file contains the following

Code:

File ID: 81
Filename: WP_20161029_16_26_49_Pro.jpg
File size 936160 (0x00000000000E48E0) bytes
Parent ID: 12
Storage ID: 0x00010001
Filetype: JPEG file

How would I obtain the File ID and the Parent ID ?

syg00 · 12-08-2016, 04:30 PM

What do you mean "from BASH" ?.
What have you tried - a simple search should provide plenty of candidates. Personally I'd be inclined to awk.

MadeInGermany · 12-11-2016, 01:23 AM

awk has the advantage of a flexible field separator.
Example

Code:

awk -F ": *" '
($1=="File ID") { print "filed=" $2 }
($1=="Parent ID") { print "parentid=" $2 }
' file

wpeckham · 12-11-2016, 11:04 AM

Quote:

Originally Posted by eco_bach

Lets say I have a file file_list.txt

This file contains the following

Code:

File ID: 81
Filename: WP_20161029_16_26_49_Pro.jpg
File size 936160 (0x00000000000E48E0) bytes
Parent ID: 12
Storage ID: 0x00010001
Filetype: JPEG file

How would I obtain the File ID and the Parent ID ?

There are, literally, DOZENS of ways that might pertain. BASH alone is not optimal for this, but there are many pattern-matching tools it can call to assist. There are also tricks using recursion and parameter lists, arrays, and cascading conditions that could be used. Might I ask what you have tried, and what you mean by 'obtain' in this context? What is your ultimate goal?

Isolating the values is one thing, how you use them once isolated is another.

Fat_Elvis · 12-11-2016, 03:15 PM

If the variables are in the same order every time, I'd do:

Code:

FILE="$(cat file_list.txt)"
FILE_ID="${FILE%%$'\n'*}"
FILE_ID="${FILE_ID##*ID: }"
PARN_ID="${FILE##*Parent ID: }"
PARN_ID="${PARN_ID%%$'\n'*}"

I'd also suggest using the above awk solution, which is probably faster than this.

szboardstretcher · 12-11-2016, 04:06 PM

If that is all that is in the file, then:

Code:

file_id=$(grep "File ID" file_list.txt|awk '{print $3}')
parent_id=$(grep "Parent ID" file_list.txt|awk '{print $3}')

eco_bach · 12-12-2016, 09:25 AM

Thanks! Going with awk

MadeInGermany · 12-12-2016, 12:49 PM

Quote:

Originally Posted by MadeInGermany

awk has the advantage of a flexible field separator.
Example

Code:

awk -F ": *" '
($1=="File ID") { print "filed=" $2 }
($1=="Parent ID") { print "parentid=" $2 }
' file

The output is shell syntax, so a simple eval assigns to shell variables

Code:

eval $(
awk -F ": *" '
($1=="File ID") { print "file_id=" $2 }
($1=="Parent ID") { print "parent_id=" $2 }
' file
)
echo $file_id
echo $parent_id