results=
results['startlogdate']="Start time"
results['endlogdate']="$finish_time"
echo "${results[*]}"
I am trying to initialise the array and adding the value to array and echo the array. The code above is my attempt.
In bash scripts, there are two kinds of arrays: numerically indexed and associatively indexed.
Depending on the version of your shell, associatively indexed arrays might not be supported.
Related to the example in your question, the correct syntax to obtain the values of the array, each as a separate word, is:
"${results[#]}"
To get the keys of the associative array, do:
"${!results[#]"
The script below demonstrates the use of an associative array. For more details, see the Arrays section in the bash manpage.
#!/bin/bash
# tst.sh
declare -A aa
aa[foo]=bar
aa[fee]=baz
aa[fie]=tar
for key in "${!aa[#]}" ; do
printf "key: '%s' val: '%s'\n" $key "${aa[$key]}"
done
echo "${aa[#]}"
exit
Here is the output:
$ bash tst.sh
key: 'foo' val: 'bar'
key: 'fee' val: 'baz'
key: 'fie' val: 'tar'
tar bar baz
Finally, I've made available my library of array functions (aka "lists"), which I've been using for many years to make managing data in arrays easy.
Check out https://github.com/aks/bash-lib/blob/master/list-utils.sh
Even if you choose not to make use of the library, you can learn a lot about arrays by reading the code there.
Good luck.
If want to use array in bash. you will be able to do in two ways.
Declare an array in bash.
declare -a Unix=('Debian' 'Red hat' 'Red hat' 'Suse' 'Fedora');
echo ${Unix[0]} # Prints the first element
echo ${Unix[*]} # prints all the elements of an array
Use directly (i.e) without declare.
Unix[0]='Debian';Unix[1]='Red hat'
finish_time=`date`
results[0]="Start time"
results[1]="$finish_time"
echo ${results[#]}
Output: Start time Wed Jan 8 12:25:14 IST 2014
Number of elements: echo ${#results[#]}
Arrays in bash are zero indexed, so ${results[0]} will be "Start time" and ${results[1]} will be "Wed Jan 8 12:25:14 IST 2014"
Related
I have a variable ($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
Say I have two associative arrays in Bash
declare -A a
declare -A b
a[xz]=1
b[xz]=2
a[zx]=3
b[zx]=4
I want to do something like this
for arr in ${a[#]} ${b[#]}; do echo ${arr[zx]}; done
and get 3 and 4 in output
but I get
$ for arr in ${a[#]} ${b[#]}; do echo ${arr[zx]}; done
1
3
2
4
Is there a way to do this in Bash?
You don't want to iterate over the contents; you want to iterate over the names of the arrays, then use indirect expansion to get the desired value of the fixed key from each array.
for arr in a b; do
t=$arr[zx] # first a[zx], then b[zx]
printf '%s\n' "${!t}"
done
Here, the variable "name" for use in indirect expansion is the name of the array along with the desired index.
Assuming the keys in both the arrays match(a major assumption), you can use one array as reference and loop over the keys and print in each array.
for key in "${!a[#]}"; do
printf "Array-1(%s) %s Array-2(%s) %s\n" "$key" "${a[$key]}" "$key" "${b[$key]}"
done
which produces an output as below. You can of-course remove the fancy debug words(Array-1, Array-2) which was added just for an understanding purpose.
Array-1(xz) 1 Array-2(xz) 2
Array-1(zx) 3 Array-2(zx) 4
One general good practice is always quote (for key in "${!a[#]}") your array expansions in bash, so that the elements are not subjected to word-splitting by the shell.
I'm trying to understand a shell script written by a previous group member. there is this for loop. I can understand it's looping through a list ${!mylist[#]} but I've only seen ${mylist[#]} before, not ${!mylist[#]}.
What does the exclamation mark do here?
for i in ${!mylist[#]};
do
echo ${mylist[i]}
....
done
${!mylist[#]} returns the keys (or indices) to an an array. This differs from ${mylist[#]} which returns the values in the array.
As an example, let's consider this array:
$ arr=(abc def ghi)
In order to get its keys (or indices in this case):
$ echo "${!arr[#]}"
0 1 2
In order to get its values:
$ echo "${arr[#]}"
abc def ghi
From man bash:
It is possible to obtain the keys (indices) of an array as well
as the values. ${!name[#]} and ${!name[*]} expand to the indices
assigned in array variable name. The treatment when in double quotes
is similar to the expansion of the special parameters # and * within
double quotes.
Example using associative arrays
To show that the same applies to associative arrays:
$ declare -A Arr=([a]=one [b]=two)
$ echo "${!Arr[#]}"
a b
$ echo "${Arr[#]}"
one two
I am currently learning shell scripting and need your help!
> array = [{u'name': u'androidTest', u'arn': u'arn:XXX', u'created':
1459270137.749}, {u'name': u'android-provider2016-03-3015:23:30', u'arn':XXXXX', u'created': 1459365812.466}]
I have a list of dictionary and want to extract the arn value from the dictionary. In python it is pretty simple for example:
for project in array:
print project['arn']
How will I write the equivalent loop in bash? If I try something like this, it is not working:
for i in "$array"
do
echo $i['arn']
done
The suggested duplicate is for associative arrays, not a list of associative arrays.
Bash can't nest data structures, so the thing that would correspond to the list of dictionaries doesn't exist natively. Using a relatively recent Bash (4.3 or newer), we can achieve something similar with namerefs:
# Declare two associative arrays
declare -A arr1=(
[name]='androidTest'
[arn]='arn:XXX'
[created]='1459270137.749'
)
declare -A arr2=(
[name]='android-provider2016-03-3015:23:30'
[arn]='XXXXX'
[created]='1459365812.466'
)
# Declare array of names of associative arrays
names=("${!arr#}")
# Declare loop variable as nameref
declare -n arr_ref
# Loop over names
for arr_ref in "${names[#]}"; do
# Print value of key 'arn'
printf "%s\n" "${arr_ref[arn]}"
done
This returns
arn:XXX
XXXXX
for project in $array
do
echo $project{'arn'}
done
Or in one line:
for project in $array; do echo $project{'arn'}; done
After thoroughly searching for a way to create an associative array in bash, I found that declare -A array will do the trick. But the problem is, it is only for bash version 4 and the bash version the server has in our system is 3.2.16.
How can I achieve some sort of associative array-like hack in bash 3? The values will be passed to a script like
ARG=array[key];
./script.sh ${ARG}
EDIT: I know that I can do this in awk, or other tools but strict bash is needed for the scenario I am trying to solve.
Bash 3 has no associative arrays, so you're going to have to use some other language feature(s) for your purpose. Note that even under bash 4, the code you wrote doesn't do what you claim it does: ./script.sh ${ARG} does not pass the associative array to the child script, because ${ARG} expands to nothing when ARG is an associative array. You cannot pass an associative array to a child process, you need to encode it anyway.
You need to define some argument passing protocol between the parent script and the child script. A common one is to pass arguments in the form key=value. This assumes that the character = does not appear in keys.
You also need to figure out how to represent the associative array in the parent script and in the child script. They need not use the same representation.
A common method to represent an associative array is to use separate variables for each element, with a common naming prefix. This requires that the key name only consists of ASCII letters (of either case), digits and underscores. For example, instead of ${myarray[key]}, write ${myarray__key}. If the key is determined at run time, you need a round of expansion first: instead of ${myarray[$key]}, write
n=myarray__${key}; echo ${!n}
For an assignment, use printf -v. Note the %s format to printf to use the specified value. Do not write printf -v "myarray__${key}" %s "$value" since that would treat $value as a format and perform printf % expansion on it.
printf -v "myarray__${key}" %s "$value"
If you need to pass an associative array represented like this to a child process with the key=value argument representation, you can use ${!myarray__*} to enumerate over all the variables whose name begins with myarray__.
args=()
for k in ${!myarray__*}; do
n=$k
args+=("$k=${!n}")
done
In the child process, to convert arguments of the form key=value to separate variables with a prefix:
for x; do
if [[ $x != *=* ]]; then echo 1>&2 "KEY=VALUE expected, but got $x"; exit 120; fi
printf -v "myarray__${x%%=*}" %s "${x#*=}"
done
By the way, are you sure that this is what you need? Instead of calling a bash script from another bash script, you might want to run the child script in a subshell instead. That way it would inherit from all the variables of the parent.
Here is another post/explanation on associative arrays in bash 3 and older using parameter expansion:
https://stackoverflow.com/a/4444841
Gilles' method has a nice if statement to catch delimiter issues, sanitize oddball input ...etc. Use that.
If you are somewhat familiar with parameter expansion:
http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
To use in your scenario [ as stated: sending to script ]:
Script 1:
sending_array.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
bash ./receive_arr.sh "${ARRAY[#]}"
Script 2: receive_arr.sh
argAry1=("$#")
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
process_arr argAry1[#]
exit 0
Method 2, sourcing the second script:
Script 1:
sending_array.sh
source ./receive_arr.sh
# A pretend Python dictionary with bash 3
ARRAY=( "cow:moo"
"dinosaur:roar"
"bird:chirp"
"bash:rock" )
process_arr ARRAY[#]
Script 2: receive_arr.sh
function process_arr () {
declare -a hash=("${!1}")
for animal in "${hash[#]}"; do
echo "Key: ${animal%%:*}"
echo "Value: ${animal#*:}"
done
}
References:
Passing arrays as parameters in bash
If you don't want to handle a lot of variables, or keys are simply invalid variable identifiers, and your array is guaranteed to have less than 256 items, you can abuse function return values. This solution does not require any subshell as the value is readily available as a variable, nor any iteration so that performance screams. Also it's very readable, almost like the Bash 4 version.
Here's the most basic version:
hash_index() {
case $1 in
'foo') return 0;;
'bar') return 1;;
'baz') return 2;;
esac
}
hash_vals=("foo_val"
"bar_val"
"baz_val");
hash_index "foo"
echo ${hash_vals[$?]}
More details and variants in this answer
You can write the key-value pairs to a file and then grep by key. If you use a pattern like
key=value
then you can egrep for ^key= which makes this pretty safe.
To "overwrite" a value, just append the new value at the end of the file and use tail -1 to get just the last result of egrep
Alternatively, you can put this information into a normal array using key=value as value for the array and then iterator over the array to find the value.
This turns out to be ridiculously easy. I had to convert a bash 4 script that used a bunch of associative arrays to bash 3. These two helper functions did it all:
array_exp() {
exp=${#//[/__}
eval "${exp//]}"
}
array_clear() {
unset $(array_exp "echo \${!$1__*}")
}
I'm flabbergasted that this actually works, but that's the beauty of bash.
E.g.
((all[ping_lo] += counts[ping_lo]))
becomes
array_exp '((all[ping_lo] += counts[ping_lo]))'
Or this print statement:
printf "%3d" ${counts[ping_lo]} >> $return
becomes
array_exp 'printf "%3d" ${counts[ping_lo]}' >> $return
The only syntax that changes is clearing. This:
counts=()
becomes
array_clear counts
and you're set. You could easily tell array_exp to recognize expressions like "=()" and handle them by rewriting them as array_clear expressions, but I prefer the simplicity of the above two functions.