Get Values out of String in bash

Question

I hope you can help me. I try to separate a String:

#!/bin/bash


file=$(<sample.txt)
echo "$file"

The File itself contains Values like this:

(;FF[4]GM[1]SZ[19]CA[UTF-8]SO[sometext]BC[cn]WC[ja]

What I need is a way to extract the Values between the [ ] and set them as variables, for Example:

$FF=4
$GM=1
$SZ=19
and so on

However, some Files do not contain all Values, so that in some cases there is no FF[*]. In this case the Program should use the Value of "99"

How do I have to do this?

Thank you so much for your help. Greetings Chris

Do you know any other languages more suitable for such things? Such as Perl, Python, or Ruby? — greut
– greut, Commented Jun 12, 2014 at 12:29

fedorqui · Accepted Answer · 2014-06-12 12:38:11Z

1

It may be a bit overcomplicated, but here it comes another way:

grep -Po '[-a-zA-Z0-9]*' file | awk '!(NR%2) {printf "declare %s=\"%s\";\n", a,$0; next} {a=$0} | bash

By steps

Filter file by printing only the needed blocks:

$ grep -Po '[-a-zA-Z0-9]*' a
FF
4
GM
1
SZ
19
CA
UTF-8
SO
sometext
BC
cn
WC
ja

Reformat so that it specifies the declaration:

$ grep -Po '[-a-zA-Z0-9]*' a | awk '!(NR%2) {printf "declare %s=\"%s\";\n", a,$0; next} {a=$0}' 
declare FF="4";
declare GM="1";
declare SZ="19";
declare CA="UTF-8";
declare SO="sometext";
declare BC="cn";
declare WC="ja";

And finally pipe to bash so that it is executed.

Note 2nd step could be also rewritten as

xargs -n2 | awk '{print "declare"$1"=\""$2"\";"}'

answered Jun 12, 2014 at 12:38

fedorqui

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Comments

glenn jackman · Accepted Answer · 2014-06-12 15:01:05Z

I'd write this, using ; or [ or ] as awk's field separators

$ line='(;FF[4]GM[1]SZ[19]CA[UTF-8]SO[sometext]BC[cn]WC[ja]'
$ awk -F '[][;]' '{for (i=2; i<NF; i+=2) {printf "%s=\"%s\" ", $i, $(i+1)}; print ""}' <<<"$line"
FF="4" GM="1" SZ="19" CA="UTF-8" SO="sometext" BC="cn" WC="ja"

Then, to evaluate the output in your current shell:

$ source <(!!)
source <(awk -F '[][;]' '{for (i=2; i<NF; i+=2) {printf "%s=\"%s\" ", $i, $(i+1)}; print ""}' <<<"$line")
$ echo $SO
sometext

To handle the default FF value:

$ source <(awk -F '[][;]' '{
   print "FF=99"
   for (i=2; i<NF; i+=2) printf "%s=\"%s\" ", $i, $(i+1)
   print ""
}' <<< "(;A[1]B[2]")
$ echo $FF
99
$ source <(awk -F '[][;]' '{
   print "FF=99"
   for (i=2; i<NF; i+=2) printf "%s=\"%s\" ", $i, $(i+1)
   print ""
}' <<< "(;A[1]B[2]FF[3]")
$ echo $FF
3

konsolebox · Accepted Answer · 2014-06-12 12:40:58Z

0

Per your request:

while IFS=\[ read -r A B; do
    [[ -z $B ]] && B=99
    eval "$A=\$B"
done < <(exec grep -oE '[[:alpha:]]+\[[^]]*' sample.txt)

Although using an associative array would be better:

declare -A VALUES

while IFS=\[ read -r A B; do
    [[ -z $B ]] && B=99
    VALUES[$A]=$B
done < <(exec grep -oE '[[:alpha:]]+\[[^]]*' sample.txt)

There you could have access both with keys ("${!VALUES[@]}") and values "${VALUES['FF']}".

edited Jun 12, 2014 at 12:40

answered Jun 12, 2014 at 12:30

konsolebox

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2 Comments

scragar Over a year ago

Might I suggest replacing eval with declare, eval can do a lot of damage with malicious input, worst declare can do it override an enviromental variable for the sake of the session.

konsolebox Over a year ago

At this point eval is safe. And in case of declaration mistakes I don't see any difference with either form of declarations. declare just creates a silent error but it's still a scripting mistake. What's more is that declare defines values to variables as local to the function by default. -g option has also only been available in 4.2.

twalberg · Accepted Answer · 2014-06-12 14:46:26Z

0

I would probably do something like this:

set $(sed -e 's/^(;//' sample.txt | tr '[][]' ' ')
while (( $# > 2 ))
do
  varname=${1}
  varvalue=${2}

  # do something to test varname and varvalue to make sure they're sane/safe

  declare "${varname}=${varvalue}"

  shift 2
done

edited Jun 12, 2014 at 14:46

answered Jun 12, 2014 at 14:30

twalberg

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