However, I find that things like: echo "fruit[$t] = '${fruit[${t}]}'; fruit[p]=${fruit[p]}." Default variable test/expansion rules apply: $ declare -A ax; Now, I have my task cut out. Thanks david, good point. This site uses Akismet to reduce spam. Before ending I want to point out another feature that I just recently discovered 1. cat /tmp/fruit | while read line; do x=3; done ... You can now use full-featured associative arrays. A value can appear more than once in an array. echo 1 | awk ‘{ sorex[“W”] declare: usage: declare [-afFirtx] [-p] [name[=value] …], using the quotes around the values throws an error like this: Notify me of followup comments via e-mail. There's nothing too surprising about associative arrays in bash, There is another solution which I used to pass variables to functions. If not pre-declared, then your example (if NOT preceded by "declare -A"): implicitly performs arithmetic evaluation of the expression "foo", which produces a numeric result of "0", thereby assigning element "0" of *indexed* array "MYMAP". To use associative arrays, you need […] Keys are unique and values can not be unique. Each key in the array can only appear once. Create an array The first thing to do is to distinguish between bash indexed array and bash associative array. For example, two persons in a list can have the same name but need to have different user IDs. Associative arrays. Hope that helped (someone) this font is so small i can hardly read it for some reason today, so if i made a mistake that’s why ( too lazy to zoom :) ) <- double chin! After following this tutorial you should be able to understand how bash arrays work and how to perform the basic operations on them. An associative array lets you create lists of key and value pairs, instead of just numbered values. arr=”$(declare -p $1)” ; eval “declare -A f=”${arr#*=}; Associative arrays seem to be local by default when declared inside a function body, where they should be global. KEYS=(${!MYMAP[@]}). The best solution probably is, as already been pointed out, to iterate through the array and copy it step by step. The indices do not have to be contiguous. In bash, array is created automatically when a variable is used in the format like, name[index]=value. An associative array is an array which uses strings as indices instead of integers. Thanks for any clarification. Running Dojo 1.7+ DOH unit tests on the command line with Rhino, Running Dojo DOH tests in a browser without a web server, Limiting the number of open sockets in a tokio-based TCP listener, Recommendation against the use of WhatsApp in your company, Streaming video with Owncast on a free Oracle Cloud computer, Linux Journal: Associative Arrays in Bash, Superuser: Test if element is in array in Bash, Stackoverflow: How to iterate over associative array in bash, https://www.gnu.org/software/gawk/manual/gawk.html, Bash association arrays | Jacek Kowalczyk MyBlog, Mac OS X Bash – upgrade – Open Source Refinery, https://blog.prakhar.info/array-basics-shell-script/. In zsh, before you can use a variable as an associative array, you have to declare it as one with. © 2020 Slashdot Media, LLC. The following doesn’t work as I expect. x=2 Funnily, there's a memoized version of keyhash you can write which uses an array … You’re only checking the version of the bash which is found first in your path, not necessarily the one you’re currently running. san francisco. 2> Create a new assoc array from indexed array where values are keys. Bash, however, includes the ability to create associative arrays, and it treats these arrays the same as any other array. Text: Write an example that illustrates the use of bash arrays and associative arrays. Copying associative arrays is not directly possible in bash. Getting started with Bash; Aliasing; Arrays; Associative arrays; Avoiding date using printf; Bash Arithmetic; Bash history substitutions; Bash on Windows 10; Bash Parameter Expansion; Brace Expansion; Case statement; CGI Scripts; Chain of commands and operations; ... Count associative array elements. otherwise keys with spaces would split to separate array items. Bash Arrays# One dimensional array with numbered index and associative array types supported in Bash. I wish I had found it before I spent an hour figuring it out myself. Basically what ${array[key]+abc} does is. item=([0]=”two”). You can think of it as a unique ID for a user in a list. item=([0]=”two”), >item=( [0]=”one” [0]=”two ) unset MYMAP[‘$K’]. Note: bash version 4 only. Andy: Copying associative arrays is not directly possible in bash. Your email address will not be published. 1. flap -> three four Bash Array – An array is a collection of elements. A detailed explanation of bash’s associative array Bash supports associative arrays. * //’); \ Just arrays, and associative arrays (which are new in Bash 4). see if the item is what we expect it to be. A clear HowTo. :-). Numerically indexed arrays can be accessed from the end using negative indices, the index of -1references the last element. Bas… fruit[a] = 'apple' Creating Arrays. bash. I am totally confused, it works, it inits and declares, it’s simple you can see the values but well… it’s like an awk 1 to me??? An associative array can be thought of as a set of two linked arrays -- one holding the data, and the other the keys that index the individual elements of the data array. Hi Craig, thanks for the very informative addition. Bash does not support multidimensional arrays. where $DB_NAME is the variable pointing to DB name string. All rights reserved. The bash man page has long had the following bug listed: unset MYMAP[“$K”], However, this one does work: You can also subscribe without commenting. Thanks for the write up but would you consider wrapping “bash version 4 only” at the start of the article in strong tags? If you want ordering, you don't use associative arrays. And it apparently stays in local scope too. Bash provides one-dimensional indexed and associative array variables. then allowed me to discover the associative array feature. Declaring an Array and Assigning values. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. HOW DOES THIS WORK WITHOUT AN ASSIGN??? fruit[a]= Loop through all key/value pair. A detailed explanation of bash’s associative array Bash supports associative arrays. Associative arrays are stored in a 'hash' order. Now, you know how to print all keys and all values so looping through the array will be easy! fruit[b] = ‘banana’; fruit[p]=pumpkin. There is NO WARRANTY, to the extent permitted by law. Defining the array. You can assign values to arbitrary keys: $ declare -A userdata Arrays are variable that hold more than one value. Using GNU bash, version 4.2.25(1)-release (x86_64-pc-linux-gnu). In order to get the scope to work how you expect, @Dave, you need to invert the operations. To destroy, delete, or … You could use the same technique for copying associative arrays: https://blog.prakhar.info/array-basics-shell-script/, declare -A MYMAP doesn’t work and throws an error: then read on. Hi Sharon, I don’t actually know why I added +_ – I am wondering whether this is an artefact of copying and pasting from somewhere else… Thanks for the comment! bash-4.1$ for key in “${sorted_keys[@]}”; do echo “$key: ${ARY[$key]}”; done Concepts: Bash arrays and associative arrays. You can only use the declare built-in command with the uppercase “-A” option.The += operator allows you to append one or multiple key/value to an associative Bash array. bash. Bash arrays. I would prefer it phrased less rudely though. One would expect that the if test would succeed both times, however it does not: You can see the problem if you add the following to the end of Bash, however, includes the ability to create associative arrays, and it treats these arrays the same as any other array. in the above example, if the variables $item1 and $item2 are un[define]d, then the result would be: this happened because undeclared variables have an implicit value of 0 when used as an indexer, it would be so these two lines are identical: >item=( [item1]=”one” [item2]=”two ) Learn how your comment data is processed. It caught me before falling into a few pitfalls: you have predictive mind. Bash print associative array. Required fields are marked *. To explicitly declare a … An associative array lets you create lists of key and value pairs, instead of just numbered values. An associative array is an array which uses strings as indices instead of integers. Also, there is no need to declare the size of an array in advance – arrays can expand/shrink at runtime. Creating associative arrays. Associative arrays are always unordered, they merely associate key-value pairs. $ bash –version A common use is for counting occurrences of some strings. I make it a habit to use “shopt -o -s nounset” in my scripts. code-bloat at its finest and just think the bash folks are exaggerating a bit, The way you have written the examples is just as one developer talks to another.. #!/ bin/bash # array-strops.sh: String operations on arrays. item=( [12]=”one” [24]=”two ), >echo ${item[12]} An associative array can be thought of as a set of two linked arrays -- one holding the data, and the other the keys that index the individual elements of the data array. The indices do not have to be … Simple, neat, to the point. Bash Associative Array (dictionaries, hash table, or key/value pair) You cannot create an associative array on the fly in Bash. Add values to arrays – note the possibility to add values to arrays with += operator. It is also worth noting that one limitation of a BASH arrays is that you cannot create a multidimensional array, such as placing an array within an array. list of items. To create an … Here's one I did for an associative array I called master_array: master_array["group_list"]+="${new_group}"; To sequence through the groups in the order you added them, sequence through the group_list field in a for loop, then you can access the group fields in the associative array. fruit[c]= In this example, authors with the same associative array value will be output by reverse order of name. This is something a lot of people missed. BASH associative array printing, I think you're asking two different things there. Unlike in many other programming languages, in bash, an array is not a collection of similar elements. I used to do a lot of bash+cmdline-perl (perl -e) to do what a simple ass.array in bash could have done. #!/bin/bash f() { declare -A map map[x]=a map[y]=b } f echo x: ${map[x]} y: ${map[y]} produces the output: x: y: while this. bash-4.1$ IFS=$’\n’ sorted_keys=( $( echo -e “${keys[@]/%/\n}” | sed -r -e ‘s/^ *//’ -e ‘/^$/d’ | sort ) ) "It's too big and too slow" (at the very bottom of the man page). Furthermore, if the values of $item1 and $item2 were not integers (strings), the values would go back to being implicitly 0 again. bash added support for associative arrays decades later, copied the ksh93 syntax, but not the other advanced data structures, and doesn't have any of the advanced parameter expansion operators of zsh. Then the loop executes one more time. Assignments are then made by putting the "key" inside the square brackets rather than an array index. Bash associative array. To access the last element of a numeral indexed array use the negative indices. Is there a way to make bash print this info without the loop? Most shells offer the ability to create, manipulate, and query indexed arrays. A simple address database A few Bourne-like shells support associative arrays: ksh93 (since 1993), zsh (since 1998), bash (since 2009), though with some differences in behaviour between the 3. As already pointed out, there is no mistake. In bash, you could use the quoted list approach mentioned in the zsh using printf %q or with newer versions ${var@Q}. Associative array. Re Missing Keys and the “+_” in the examples: this is in fact quite important, and it’s a good thing you quoted it in this guide. is not true for bash versions <4.2 wherein associative arrays MUST be explicitly created with "declare -A". I normally create an indexed array from the sql query result as below: done < /tmp/fruit, echo "" #!/bin/bash OFS=$IFS # store field separator IFS="${2: }" # define field separator file=$1 # input file name unset a # reference to line array unset i j # index unset m n # dimension ### input i=0 while read line do a=A$i unset $a declare -a $a='($line)' i=$((i+1)) done < $file # store number of lines m=$i ### output for ((i=0; i < $m; i++)) do a=A$i # get line size # double escape '\\' for sub shell '``' and 'echo' n=`eval … Note: bash 4 also added associative arrays, but they are implemented slightly differently. #!/bin/bash Associative arrays (sometimes known as a "hash" or "dict") use arbitrary nonempty strings as keys. b banana The bash man page has long had the following bug listed: "It's too big and too slow" (at the very bottom of the man page). ... Bash Array Declaration. There is another solution which I used to pass variables to functions. echo $x. $ declare -A foo[“flap”]=”three four” foo[“flop”]=”one two” (In bash 4 you can use declare -g to declare global variables - but in bash 4, you should be using associative arrays … Print the entire array content. bash arrays and associative arrays This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. There is no one single true way: the method you'll need depends on where your data comes from and what it is. FRUITS, while read t f; do $ echo ${ax[foo]:+SET}; echo “fruit[a]=${fruit[‘a’]}” flop -> one two. | while read line; \ fruit[p]=pumpkin To use Sharon’s example, this indeed seems to work: # if [ ${MYMAP[blablabla]} ]; then echo yes; else echo no;fi I’m jealous of this. A few Bourne-like shells support associative arrays: ksh93 (since 1993), zsh (since 1998), bash (since 2009), though with some differences in behaviour between the 3. On the other hand, if you've ever used any modern Office Suite and seen for (i in sorex) print i }’, Hi Mark, that code inside the single quotes is all Awk code, not bash. In BASH script it is possible to create type types of array, an indexed array or associative array. So in that subprocess, the variables are being set, but when the while loop terminates the subprocess terminates and the changes to the variables are lost. Extending the answer from @AndrewSchulman, using -rn as a global sort option reverses all columns. This might help: https://www.gnu.org/software/gawk/manual/gawk.html. Since bash does not discriminate string from a number, an array can contain a mix of strings and numbers. The last field in the Iplogs.txt is … Note: bash 4 also added associative arrays, but they are implemented slightly differently. $ /tmp/t.bash In plain English, an indexed array is a list of things prefixed with a number. the script to print out all the keys: You can see here that the first assignment, the one done via the declare -A userinfo This will tell the shell that the userinfo variable is an associative array. one You can use any string or integer as a subscript to access array elements.The subscripts and values of associative arrays are called key value pairs. Multidimensional arrays are not supported, but can be simulated using associative arrays. If you're looking for a shell with better associative array support, try zsh. Or, you use a non-associative array as well as an associative array. Bash supports one-dimensional numerically indexed and associative arrays types. GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu) String operations on arrays. Bash provides support for one-dimensional numerically indexed arrays as well as associative arrays. It is important to remember that a string holds just one element. bash-4.1$, Hi CPRitter, that looks like a pretty good way to do this, but I think at this point I’d be reaching for Perl or Python…. echo “fruit[$t] = ‘${fruit[${t}]}’; fruit[p]=${fruit[p]}.” ; \ 1> how to convert a nornal array (indexed array with index starting at 0) into an associative array where value becomes a key and value itself is the value. This is important because many programmers expect that because integer arrays are implicit, that the associative arrays _should be_ too. Those are referenced using integers and associative are referenced using strings. list incorrectly adds the key as a\ b rather than simply as a b. An associative array is an array of named keys instead of index values. :) I just bashed (cough) my head against the keyboard for 10 minutes because I’m on bash 3.2.8 (OSX 10.7.5). >declare -p item Bash associative array key exists. echo “c cranberry” >> /tmp/fruit, declare -A fruit mobble: mibble Bash Arrays# One dimensional array with numbered index and associative array types supported in Bash. If you agree with that, then you probably won't want to read about the "new" associative arrays that were added in version 4.0 of bash. Unlike most of the programming languages, Bash array elements don’t have to be of the same data type. It differentiates between the case where a key does not exist, and the case where it does exist but its value is null. Bash & ksh: echo ${MYARRAY[@]} Print all keys. There are two types of arrays you can use – indexed and associative arrays. Bash Arrays # Bash supports one-dimensional numerically indexed and associative arrays types. It works for me without this addition: fruit[c] = ‘cranberry’; fruit[p]=pumpkin. Let’s define an array of names. Even though I explicitly declare fruit to be an associative array, and it acts like it inside the while loop, the values added during the loop are not present outside the loop. Quick reference of things I discovered about how to use associative arrays in bash. I know it can very well be done using a loop but for a huge sized array containing almost 500,000 elements, In those cases, hopefully the habit of doing it in scripts rubs off on you enough to have it done in the interactive ones as well :). Arrays. The following code. $. check out my earlier post. Hi Dave, if you set a variable value inside the do .. done it does not leak out of the scope: $ cat /tmp/t.bash There's nothing too surprising about associative arrays in bash, they are as you probably expect: declare -A aa aa [ hello ]= world aa [ ab ]=cd The -A option declares aa to be an associative array. Bash & ksh: echo “a apple” > /tmp/fruit Sorry you can’t use it! unset MYMAP[” “] As mentioned earlier, BASH provides three types of parameters: Strings, Integers and Arrays. declare -A aa Declaring an associative array before initialization or use is mandatory. Here's my little guide on how to define and access associative arrays in bash. Bash 4 supports associative arrays, yay! Text: Write an example that illustrates the use of bash arrays and associative arrays. I found the rest of the article quite good, so it was a disappointment to see this tip at the end. To access the last element of a numeral indexed array … grabble: gribble do \ All You can think of an array is a variable that can store multiple variables within it. about bash arrays: the ability to extend them with the += operator. You can assign values to arbitrary keys: $ Bash supports both regular arrays that use integers as the array index, and associative arrays, which use a string as the array index. Just to recap: associative arrays are arrays with named key value pairs. Passing to a function and how to assign between variables (both arrays) is missing IMHO. echo “fruit[b]=${fruit[‘b’]}” Combine Bash associative arrays. fribble: frabble done. AWK has associative arrays and one of the best thing about it is – the indexes need not to be continuous set of number; you can use either string or number as an array index. Avi, are you sure you are using bash? As you can see on the second line, the index ‘0’ gets defined twice, of course the last being the final value for that index. Associative arrays are an abstract data type that can be considered as dictionaries or maps. Example $ declare -p MYMAP In zsh, before you can use a variable as an associative array, you have to declare it as one with. done. fruit[b] = 'banana' unset MYMAP[‘ ‘] For the benefit of future visitors to this page (like me) that are running pre-4.2 bash, the comment in your statement: “$ MYMAP[foo]=bar # Or this line implicitly makes it an associative array (in global scope)”. #Declare array. Now, I was brought to your site while searching for a solution to this …, Is there a less clumsy method of sorting keys than this (spaces in keys must be preserverd)…, bash-4.1$ declare -A ARY=( [fribble]=frabble [grabble]=gribble [co bb le]=cribble [babble]=bibble [zibble]=zabble [n o bbl e]=nibble [mobble]=mibble ) Also, if K is a single or double quote, only the latter one works! a loop is an overhead. a apple Bash's history commands are unmatched by any other shell (Zsh comes close, but lacks some options, such as the ability to delete by line number). is not the way to check the version of your current bash? for i in "${!fruit[@]}"; do Hi Matteo, thanks – yes those would be useful. This is actually the thing that lead me to the man page which Those are referenced using integers and associative are referenced using strings. fruit[b]= You can also assign multiple items at once: You can also use keys that contain spaces or other "strange" characters: Note however that there appears to be a bug when assigning more than one >item=( [item1]=”one” [item2]=”two ), > declare -p item Concepts: Bash arrays and associative arrays. Don't subscribe In an associative array the key is written as a string, therefore we can associate additional information with each entry in the array. Thank you very much for such a priceless post. t=$(echo $line|sed -e ‘s/ . using a "direct" assignment. Declare an associative array. In this article, we will explain how you can declare and initialize associative arrays in Linux bash. Arrays the same as any other array tried declare -A associative_array … 6.7 arrays the key... T work as I expect within it true for bash versions < 4.2 wherein arrays! ’ t have to be, still writing free Software ; you are free change! Need depends on where your data comes from and what it is important to that... Important to remember that a string, therefore we can use a variable is used in the can! `` 0 '', not the string `` foo '' single space without the loop same. Do n't use associative arrays, via this very handy page indexing ” section KEYS=! Section example KEYS= ( $ { array [ 2 ] etc., Awk associative printing! Variables to functions is to distinguish between bash indexed array ; the declare builtin will explicitly an... 6.7 arrays important to remember that a string holds just one element from and what it is important many! Writing free Software, Moon picture Albuquerque Moon by Jason Bache, used under CC-BY-2.0 putting ``. This will tell the shell that the userinfo variable is used in the following doesn ’ t as. Of elements 'hash ' order and query indexed arrays via typeset -A bash associative array of arrays can! To look up a value from a number value pairs, instead just... Statement tests to see if the item is what we expect it to be addition... String from a table based upon its corresponding string label an assoc array from the end and values. Same name but need to declare bash associative array of arrays as one with is possible to create arrays. – yes those would be useful index of the most used parameter type from and what is. Associative are referenced using strings use negative indices, the index of the.... Informative addition information with each entry in the array is dynamic ( i.e to create type of! And Ksh93 assigned contiguously ) 3. bash array – an array is not directly possible in bash 4 added! Can be declared, so that memory will be output by reverse order of name do lot. An hour figuring it out myself and support for multi-dimensional arrays does exist but its value is null userinfo! Unset an array, nor any requirement that members be indexed or assigned contiguously one! Declare all variables same data type is created automatically when a variable key from an associative the. Your current bash -A MYMAP here and it treats these arrays the same technique for copying associative arrays, query... Open Source community since bash does not discriminate string from a number you 're looking for a user in 'hash. See the syntax in any manual or search I ’ ve done assign between variables ( both arrays is. Other words, associative arrays those are referenced using strings n't subscribe all Replies to my Notify. Inside a function and how to use them in your bash scripts differentiates between the case where it exist... Following doesn ’ t see the syntax in any manual or search I ’ done. [ 1 ], array is a single or double quote, only the latter one works order of.... The shell that the userinfo variable is used in the order that they 're created most used parameter type –! $ ( echo $ { # aa [ @ ] } ) calculate how many sites it.... Just to recap: associative arrays types – yes those would be useful like. Sites it accessed I just tried declare -A MYMAP here and it worked are several ways can..., try zsh array of named keys instead of index values between the case where it exist!: echo `` $ { # aa [ @ ] } print all.. Where that variable may be used as an indexed array or associative array lets you lists! We expect it to be just declare all variables -A in bash 4 ), which new... One string to another bash arrays work and how to print all keys a collection of elements,... End using negative indices be simulated using associative arrays define and access associative arrays is not directly bash associative array of arrays bash., Moon picture Albuquerque Moon by Jason Bache, used under CC-BY-2.0 on.... Define and access associative arrays are stored in a 'hash ' order associative! And bash associative array value will be output by reverse order of name of elements defined! Example, authors with the rest of the array can only appear once the.. Wherein associative arrays, and explain how to use “ shopt -o -s nounset ” in my scripts ’ cover... Can contain a mix of strings: it maps integers to strings declared so! Used under CC-BY-2.0 before I spent an hour figuring it out myself ways you can create an which. Think of it as one with the current value from a number tell the shell that associative! ‘ s/, Moon picture Albuquerque Moon by Jason Bache, used under CC-BY-2.0 ] arrays used fundamental... Associative array is an array to be of the array is created automatically a... With += operator also works with regular variables and appends to the extent by! ( x86_64-pc-linux-gnu ) arrays is not a collection of similar elements capital a: here my. -A associative_array, that the associative arrays, and it worked no one true. Hi Matteo, thanks for the arrays search I ’ ve done in! Ab ) use arbitrary nonempty strings as keys of arrays, is the original magazine of the most misused type. Like array [ 1 ], array [ 1 ], array is an error in “ indexing. +Abc } does is the script the very informative addition to work fine number elements! “ shopt -o -s nounset ” in my scripts name of the used! -P MYMAP declare -A associative_array 6.7 arrays Notify me of followup comments via e-mail [ key ] +abc } is... To distinguish between bash indexed array or associative array of publication, is the original magazine of code! The script at the end using negative indices are implicit, that the userinfo variable is an associative array. ; \ f= $ ( echo $ { # aa [ @ ] } ) using assignments! As any other array or, you do n't subscribe all Replies to my comments Notify me of comments! Most misused parameter type ksh: echo `` $ {! MYMAP [ @ ] } ) languages! Address the issue and perform fundamental operations on them ] bash v4 and higher associative! Is important to remember that a string, therefore we can associate additional information with each entry the... This very handy page guide on how to define and access associative arrays be easy using GNU,. A function and how to use associative arrays types uppercase “ -A ”.! Explains everything about associative arrays types need [ … ] bash v4 and higher support associative arrays stored... As keys fixed it = 'banana ' ; fruit [ b ] = 'apple ' ; fruit [ ]... In my scripts ve done Replies to my comments Notify me of followup comments via e-mail within it will how... ] d one previously one with Creating numerically indexed array and copy it step by.. '' or `` dict '' ) use variable indirection as a means to address issue... ] bash v4 and higher support associative arrays allow you to append one or multiple key/value an! It as one with … if you want ordering, you have predictive mind b! Includes the ability to create associative arrays _should be_ too ’ ll cover the arrays! Are variable that hold more than once in an array which uses strings as instead... '' # out: 3 Destroy, Delete, or Unset an array is an associative array before initialization use. Builtin will explicitly declare an array is a list of strings: it integers. Are then made by putting the `` key '' inside the square brackets rather than array. And bash associative array value will be allocated for the very informative.... While loop needs to be of the loop the if statement tests to see this tip at the of... Used as an indexed array use the negative indices, the index of the script step! To pass variables to functions if statement tests to see if the is! In a 'hash ' order be unique can only use numbers ( more specifically, integers... With `` declare -A MYMAP= ' ( [ 0 ] = 'banana ' ; [. Fill your array with numbered index and associative arrays must be an integer number foo.! The negative indices Self-Perfection – I have bash associative array of arrays it think you 're looking for a shell with associative!, representing 25+ years of publication, is the original magazine of the code below use “ -o. Arrays should be used as an indexed array use the declare builtin will explicitly an. Created automatically when a variable as an indexed array use the same as other. ; you are free to change and redistribute it in the Iplogs.txt is …:. Publication, is the original magazine of the current value counting occurrences of some strings more on using arrays... Also very useful use is for counting occurrences of some strings etc., Awk associative array bash one-dimensional... Otherwise keys with spaces would split to separate array items use any variable as an associative implicitly a... Note also that the += operator also works with regular variables and appends the! X86_64-Pc-Linux-Gnu ) is to distinguish between bash indexed array ; the declare builtin will explicitly declare an.. Lets you create lists of key and value pairs, instead of just numbered values, they.