How can I access array elements by string?
What I want to achieve is the following: I have a number of json files in a directory. These should be read in one after the other. All key values ("id", "test") should be configured / replaced. The changes should be saved in the json files.
#a json file example:
{
"id": "<fill-id>",
"test": "<fill-test>"
}
The first key "id" should call the function "create_id".
The second key "test" should call the function "create_test".
#!/bin/sh
declare -a FUNCTION
FUNCTION["id"]="create_id"
FUNCTION["test"]="create_test"
FUNCTION["secret"]="FUNCTION.C"
# read key/value from json file
for filename in *.json; do
while read -r key value; do
declare "$key=$value"
echo name: $key value: $value
${FUNCTION[$key]} $filename $value
done < <(jq -r 'to_entries[] | "\(.key) \(.value)"' $filename)
done
You'll need to use an associative array, declare -A FUNCTION
BUT associative arrays are not a sh feature: declare -A is bash syntax. Change your #! line.
You'll also need bash version 4.0 or greater: the default /bin/bash on MacOSX is too old.
You can also find associative arrays in ksh and zsh.
Related
I have a variable ($OUTPUT) that contains the following name / value pairs:
member_id=4611686018429783292
platform=Xbox
platform_id=1
character_id=2305843009264966985
period_dt=2020-11-25 20:31:14.923158 UTC
mode=all Crucible modes
mode_id=5
activities_entered=18
activities_won=10
activities_lost=8
assists=103
kills=233
average_kill_distance=15.729613
total_kill_distance=3665
seconds_played=8535
deaths=118
average_lifespan=71.72269
total_lifespan=8463.277
opponents_defeated=336
efficiency=2.8474576
kills_deaths_ratio=1.9745762
kills_deaths_assists=2.411017
suicides=1
precision_kills=76
best_single_game_kills=-1
Each line ends with \n.
I want to loop through them, and parse them into an associative array, and the access the values in the array by the variable names:
while read line
do
key=${line%%=*}
value=${line#*=}
echo $key=$value
data[$key]="$value"
done < <(echo "$OUTPUT")
#this always prints the last value
echo ${data['seconds_played']}
This seems to work, i.e. key/value print the right values, but when I try to pull any values from the array, it always returns the last value (in this case -1).
I feel like im missing something obvious, but have been banging my head against it for a couple of hours.
UPDATE: My particular issue is I'm running a version of bash (3.2.57 on OSX) that doesn't support associative arrays). I'll mark the correct answer below.
Without declare -A data, then data is a normal array. In normal arrays expressions in [here] first undergo expansions, then arithmetic expansion. Inside arithmetic expansion unset variables are expanded to 0. You are effectively only just setting data[0]=something, because data[$key] is data[seconds_played] -> variable seconds_played is not defined, so it expands to data[0]
Add declare -A data and it "should work". You could also just:
declare -A data
while IFS== read -r key value; do
data["$key"]="$value"
done <<<"$OUTPUT"
Try declaring data as an associative array before populating it, eg:
$ typeset -A data # declare as an associative array
$ while read line
do
key=${line%%=*}
value=${line#*=}
echo $key=$value
data[$key]="$value"
done <<< "${OUTPUT}"
$ typeset -p data
declare -A data=([mode]="all Crucible modes" [period_dt]="2020-11-25 20:31:14.923158 UTC" [deaths]="118" [best_single_game_kills]="-1" [efficiency]="2.8474576" [precision_kills]="76" [activities_entered]="18" [seconds_played]="8535" [total_lifespan]="8463.277" [average_lifespan]="71.72269" [character_id]="2305843009264966985" [kills]="233" [activities_won]="10" [average_kill_distance]="15.729613" [activities_lost]="8" [mode_id]="5" [assists]="103" [suicides]="1" [total_kill_distance]="3665" [platform]="Xbox" [kills_deaths_ratio]="1.9745762" [platform_id]="1" [kills_deaths_assists]="2.411017" [opponents_defeated]="336" [member_id]="4611686018429783292" )
$ echo "${data['seconds_played']}"
8535
I'm trying to use associative arrays as a work around for Bash's poor function parameter passing. I can declare a global associative array and read/write to that but I would like to have the variable name passed to the function since many times I want to use the same function with different parameter blocks.
Various Stack Overflow posts have approaches for reading a passed array within a function but not writing to it to allow return values. Pseudo Bash for what I'm trying to do is thus:
TestFunc() {
local __PARMBLOCK__=${1} # Tried ${!1} as well
# Do something with incoming array
__PARMBLOCK__[__rc__]+=1 # Error occured
__PARMBLOCK__[__error__]+="Error in TestFunc"
}
declare -A FUNCPARM
# Populate FUNCPARM
TestFunc FUNCPARM
if [[ ${FUNCPARM[__rc__]} -ne 0 ]]; then
echo "ERROR : ${FUNCPARM[__error__]}
fi
Is this kind of thing possible or do I really need to abandon Bash for something like Python?
EDIT: Found the duplicate. This is basically the same answer as this one.
You can use a reference variable for that, see help declare:
declare [-aAfFgilnrtux] [-p] [name[=value] ...]
[...]
-n make NAME a reference to the variable named by its value
[...]
When used in a function, declare makes NAMEs local, as with the local command.
f() {
declare -n paramblock="$1"
# example for reading (print all keys and entries)
paste <(printf %s\\n "${!paramblock[#]}") <(printf %s\\n "${paramblock[#]}")
# example for writing
paramblock["key 1"]="changed"
paramblock["new key"]="new output"
}
Example usage:
$ declare -A a=(["key 1"]="input 1" ["key 2"]="input 2")
$ f a
key 2 input 2
key 1 input 1
$ declare -p a
declare -A a=(["key 2"]="input 2" ["key 1"]="changed" ["new key"]="new output" )
This works very well. The only difference to an actual associative array I found so far is, that you cannot print the referenced array using declare -p as that will only show the reference.
I want to create a dictionary in bash from a text file which looks like this:
H96400275|A
H96400276|B
H96400265|C
H96400286|D
Basically I want a dictionary like this from this file file.txt:
KEYS VALUES
H96400275 = A
H96400276 = B
H96400265 = C
H96400286 = D
I created following script:
#!/bin/bash
declare -a dictionary
while read line; do
key=$(echo $line | cut -d "|" -f1)
data=$(echo $line | cut -d "|" -f2)
dictionary[$key]="$data"
done < file.txt
echo ${dictionary[H96400275]}
However, this does not print A, rather it prints D. Can you please help ?
Associative arrays (dictionaries in your terms) are declared using -A, not -a. For references to indexed (ones declared with -a) arrays' elements, bash performs arithmetic expansion on the subscript ($key and H96400275 in this case); so you're basically overwriting dictionary[0] over and over, and then asking for its value; thus D is printed.
And to make this script more effective, you can use read in conjunction with a custom IFS to avoid cuts. E.g:
declare -A dict
while IFS='|' read -r key value; do
dict[$key]=$value
done < file
echo "${dict[H96400275]}"
See Bash Reference Manual § 6.7 Arrays.
the only problem is that you have to use -A instead of -a
-a Each name is an indexed array variable (see Arrays above).
-A Each name is an **associative** array variable (see Arrays above).
What you want to do is so named associative array. And to declare it you need to use command:
declare -A dictionary
I'm wondering if anyone can help. I've not managed to find much in the way of examples and I'm not sure where to start coding wise either.
I have a file with the following contents...
VarA=/path/to/a
VarB=/path/to/b
VarC=/path/to/c
VarD=description of program
...
The columns are delimited by the '=' and some of the items in the 2nd column may contain gaps as they aren't just paths.
Ideally I'd love to open this in my script once and store the first column as the variable and the second as the value, for example...
echo $VarA
...
/path/to/a
echo $VarB
...
/path/to/a
Is this possible or am I living in a fairy land?
Thanks
You might be able to use the following loop:
while IFS== read -r name value; do
declare "$name=$value"
done < file.txt
Note, though, that a line like foo="3 5" would include the quotes in the value of the variable foo.
A minus sign or a special character isn't allowed in a variable name in Unix.
You may consider using BASH associative array for storing key and value together:
# declare an associative array
declare -A arr
# read file and populate the associative array
while IFS== read -r k v; do
arr["$k"]="$v"
done < file
# check output of our array
declare -p arr
declare -A arr='([VarA]="/path/to/a" [VarC]="/path/to/c" [VarB]="/path/to/b" [VarD]="description of program" )'
What about source my-file? It won't work with spaces though, but will work for what you've shared. This is an example:
reut#reut-home:~$ cat src
test=123
test2=abc/def
reut#reut-home:~$ echo $test $test2
reut#reut-home:~$ source src
reut#reut-home:~$ echo $test $test2
123 abc/def
Is it possible to create an array of objects in bash?
That's how I'm trying:
declare -a identifications=(
{
email = '...',
password = '...'
}
)
declare -a years=(
'2011'
'2012'
'2013'
'2014'
'2015'
'2016'
)
for identification in "${identifications[#]}"
do
for year in "${years[#]}"
do
my_program --type=CNPJ --format=XLS --identification=${identification.email} --password=${identication.password} --competence=${year} --output="$identification - $year"
done
done
Obviously, this doesn't work, and I'm not finding how to achieve that, since I'm not finding bash objects.
You could do some trickery with associative arrays (introduced in Bash 4.0) and namerefs (see manual for declare and the first paragraph of Shell Parameters – introduced in Bash 4.3):
#!/usr/bin/env bash
declare -A identification0=(
[email]='test#abc.com'
[password]='admin123'
)
declare -A identification1=(
[email]='test#xyz.org'
[password]='passwd1!'
)
declare -n identification
for identification in ${!identification#}; do
echo "Email: ${identification[email]}"
echo "Password: ${identification[password]}"
done
This prints
Email: test#abc.com
Password: admin123
Email: test#xyz.org
Password: passwd1!
declare -A declares an associative array.
The trick is to assign all your "objects" (associative arrays) variable names starting with the same prefix, like identification. The ${!prefix#} notation expands to all variable names starting with prefix:
$ var1=
$ var2=
$ var3=
$ echo "${!var#}"
var1 var2 var3
Then, to access the key-value pairs of the associative array, we declare the control variable for the for loop with the nameref attribute:
declare -n identification
so that the loop
for identification in ${!identification#}; do
makes identification behave as if it were the actual variable from the expansion of ${!identification#}.
In all likelihood, it'll be easier to do something like the following, though:
emails=('test#abc.com' 'test#xyz.org')
passwords=('admin123' 'passwd1!')
for (( i = 0; i < ${#emails[#]}; ++i )); do
echo "Email: ${emails[i]}"
echo "Password: ${passwords[i]}"
done
I.e., just loop over two arrays containing your information.
I tend to use json to create objects. For me it makes it really easy and flexible.
Here is a oversimplified example.
I create a json file: devices.json
{
"backup" : [{
"addr":"192.168.1.1",
"username":"backuper",
"dstfile":"firewallconfig",
"ext":".cfg",
"method":"ssh",
"rotate":"no",
"enabled":"yes"
}, {
"addr":"192.168.1.2",
"username":"backuper",
"dstfile":"routerconfig",
"ext":".cfg",
"method":"ssh",
"rotate":"no",
"enabled":"yes"
}]
}
Bash script: task.sh
# read the devices.json file and store it in the variable jsonlist
jsonlist=$(jq -r '.backup' "devices.json")
# inside the loop, you cant use the fuction _jq() to get values from each object.
for row in $(echo "${jsonlist}" | jq -r '.[] | #base64'); do
_jq()
{
echo ${row} | base64 --decode | jq -r ${1}
}
echo "backing up: $(_jq '.addr')"
echo "using method: $(_jq '.method')"
Done
The guy who posted the original post can be found by googling "using json with bash" or something.