1

I'm currently stuck on how to do the following:

I have a settings file that looks like this:

USER_ID=12
ROLE=admin
STARTED=10/20/2010
...

I need to access the role and map the role to one of the variables in the script below. After I will use that variable to call open a doc with the correct name.

test.sh

#!/bin/sh

ADMIN=master_doc
STAFF=staff_doc
GUEST=welcome_doc    

echo "accessing role type"
cd /setting

#open `settings` file to access role?
#call correct service
#chmod 555 master_doc.service

Is there a way to interpolate strings using bash like there is in javascript? Also, I'm guessing I would need to traverse through the settings file to access role?

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4
  • Your script doesn't actually use any variables like $admin, so what are you trying to accomplish exactly? If admin = master_doc is supposed to be assignment, the spaces shouldn't be there. Please edit to clarify. Commented Aug 10, 2020 at 23:27
  • @wjandrea the settings has a role. That role needs to be mapped to a doc name which is then used to call a specific service. Commented Aug 10, 2020 at 23:34
  • Oh, I get what you mean. You want to get the variables from settings, use $role as an indirect reference to $admin, i.e. master_doc, then turn that into a string, master_doc.service. I'll write you answer. Commented Aug 10, 2020 at 23:35
  • @lost9123193 : There is no bash involved in your question, since your script seems to be sh, not bash. Also you did not define the syntax of your settings file. The example you povided, would be valid syntax in both sh and in bash, so a source settings would be enough to read the variables in your concrete example. Commented Aug 11, 2020 at 6:21

4 Answers 4

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5

With bash and grep and assuming that the settings file has exactly one line beginning with ROLE=:

#!/bin/bash

admin=master_doc
staff=staff_doc
guest=welcome_doc

cd /setting || exit
role=$(grep '^ROLE=' settings)
role=${role#*=}
echo chmod 555 "${!role}.service"

Drop the echo after making sure it works as intended.
Look into Shell Parameter Expansion for indirect expansion.

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2 Comments

could you explain what this means? ${role#*=}?
@lost9123193 The part from the beginning up to (and including) the first = character is deleted from the value of the variable role. Look into Shell Parameter Expansion for${parameter#word} and ${parameter##word}
3

From what I understand, you want to get the variables from settings, use $role as an indirect reference to $admin, i.e. master_doc, then turn that into a string, master_doc.service.

Firstly, instead of indirection, I recommend an associative array since it's cleaner.

You can use source to get variables from another file, as well as functions and other stuff.

Lastly, to dereference a variable, you need to use the dollar sign, like $role. Variable references are expanded inside double-quotes, so that's sort of the equivalent of string interpolation.

#!/bin/bash

# Associative array with doc names
declare -A docs=(
    [admin]=master_doc
    [staff]=staff_doc
    [guest]=welcome_doc
) 

echo "accessing role type"
cd setting || exit

source settings  # Import variables 
true "${ROLE?}"  # Exit if unset

echo chmod 555 "${docs[$ROLE]}.service"  # Select from associative array
# ^ Using "echo" to test. Remove if the script works properly.
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7 Comments

this is exactly what i was looking for! Quick question, since the associative array is going to be used quite a few places, can I add it to the settings file like this: declare -A DOC_TYPE.... and call in this file as: ${DOCT_TYPE[$ROLE]}?
@lost9123193 That would work, yeah, as long as it's only used by Bash, since associative arrays are a Bash feature, not always available in sh.
can i use sh with this script?
@lost9123193 Maybe. To be safe, no.
oh I have to use sh :/ Is this why I'm getting the error: declare: -A: invalid option?
|
0

You can source the settings file to load the variables:

source settings

And then you can use them in your script:

chmod 555 "${admin}.service"  # will replace ${admin} with master_doc
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5 Comments

The quotes around variable names are to avoid splitting parameters. For example, if your variable were x="foo bar.sh" and you then do chmod 555 $x (without quoting x), it will expand $x to chmod 555 foo bar.sh, which will try to apply chmod 555 to a file foo and another file bar.sh. If you quote it (chmod 555 "$x"), then it will correctly point to foo bar.sh (one file).
Also: you can call variables with braces or without them (so $x and ${x} are both valid). I prefer to use braces so it's easier to identify var names.
It appears you may have misunderstood the question.
@LxerLx thanks for the heads up, it seems like OP changed/added details to the question after I answered. With that said, given an example settings file like the one in this question, this answer would be valid :)
The answer is valid whenROLE=admin, but is not valid when ROLE=guest orROLE=stuff. The OP wants that the script behaves according to the value of ROLE. I still suspect you may have misunderstood the question.
0

I'd certainly use source(.)

#!/bin/sh
ADMIN=master_doc
STAFF=staff_doc
GUEST=welcome_doc

echo "accessing role type"
. /setting/settings 2> /dev/null || { echo 'Settings file not found!'; exit 1; }

role=${ROLE^^} # upercase rolename
echo ${!role}.service # test echo
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1 Comment

seems to be stuck at the first echo.

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