= arrays bash
~~NOTOC~~
{{tag>linux bash pendiente wiki}}
/via: [[http://www.thegeekstuff.com/2010/06/bash-array-tutorial/]]

<callout type="info" title="más información de interés (arrays indirection)" icon="true">http://wiki.bash-
hackers.org/syntax/arrays?rev=1534920675</callout>
<callout type="info" title="más información de interés (arrays asociativos)" icon="true">https://www.artificialworlds.net/blog/2012/10/17/bash-associative-array-examples/</callout>

== declaración e inicialización
<code bash; indices numéricos>
declare -a array=(valor0 'valor uno' 'valor dos')
</code>
<code bash; asociativo>
declare -A array=( [indice1]=valor0 [indice2]='valor uno' [indice3]='valor dos')
# es necesario una versión 4+ de BASH para disponer de Arrays asociativos
</code>


== declaración y asignación
<code bash>
array=(valor0 'valor uno' 'valor dos')
</code>
<code bash>
array[0]='valor0'
array[1]='valor uno'
array[2]='valor dos'
</code>

== + asignaciones
<code bash>
array[n]=valor
array[cadena]=valor
array=valor # se asigna al índice 0 (en asociativos, a "0")
array=(valor1 valor2 valor3)
array=([0]=valor1 1=valor2 2=valor3)
array=([cadena]=valor1 [cadena2]=valor2)
array+=(valor5 valor6) # añade
array=("${otro_array[@]}")
</code>

== recuperación
^Sintaxis ^ Descripción ^
| **${ARRAY[N]}** | recupera el elemento N  |
| **${ARRAY[S]}** | recupera el elemento S en arrays **asociativos** |
| **"${ARRAY[@]}"** | \\ Recupera todos los elementos\\ Si está entrecomillado, @ devuelve cada elemento, %%*%% devuelve un único resultado con todos los elementos.\\ Si no lo está, las dos devuelven lo mismo |
| **${ARRAY[@]}** | ::: |
| ** "${ARRAY[*]}"** | ::: |
| **${ARRAY[*]}** | ::: |
| **"${ARRAY[@]:N:M}"** | \\ De funcionamiento similar a la regla anterior, añade que devuelve desde el elemento N, M elementos |
| **${ARRAY[@]:N:M}** | ::: |
| **"${ARRAY[*]:N:M}"** | ::: |
| **${ARRAY[*]:N:M}** | ::: |

=== mostar array/elementos/subcadenas
  * todo el array: ''echo ${array[@]}''
  * un elemento: ''echo ${array[n]}''
  * del elemento n al m: ''echo ${array[@]:n:m}''
  * del elemento n, subcadena a-b: ''echo ${array[n]:a:b}''
  * todos los items del array: ''${array[*]}''
  * todos los índices del array:  ''${!array[*]}''
  * número de items:  ''${#array[*]}''
  * vía: [[http://www.linuxjournal.com/content/bash-arrays]]

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^Syntax ^Description ^
| **${ARRAY[N]}** | Expands to the value of the index ''N'' in the **indexed** array ''ARRAY''. If ''N'' is a negative number, it's treated as the offset from the maximum assigned index (can't be used for assignment) - 1  |
| **${ARRAY[S]}** | Expands to the value of the index ''S'' in the **associative** array ''ARRAY''. |
| **"${ARRAY[@]}"\\ ${ARRAY[@]}\\ "${ARRAY[*]}"\\ ${ARRAY[*]}** | Similar to [[scripting:posparams#mass_usage| mass-expanding positional parameters]], this expands to all elements. If unquoted, both subscripts ''*'' and ''@'' expand to the same result, if quoted, ''@'' expands to all elements individually quoted, ''*'' expands to all elements quoted as a whole. |
| **"${ARRAY[@]:N:M}"\\ ${ARRAY[@]:N:M}\\ "${ARRAY[*]:N:M}"\\ ${ARRAY[*]:N:M}** | Similar to what this syntax does for the characters of a single string when doing [[syntax:pe#substring_expansion| substring expansion]], this expands to ''M'' elements starting with element ''N''. This way you can mass-expand individual indexes. The rules for quoting and the subscripts ''*'' and ''@'' are the same as above for the other mass-expansions. |

</collapse>
== metadata
^ Syntaxis ^Descripción ^
|**${#ARRAY[N]}** | Longitud del elemento N |
|**${#ARRAY[STRING]}** | idem en **asociativo** |
|**${#ARRAY[@]}**\\ **${#ARRAY[*]}**| Número de elementos |
|**${!ARRAY[@]}**\\ **${!ARRAY[*]}**| Extrae los índices del array, @ elemento a elemento, %%*%% en un bloque (desde BASH 3.0)|

=== longitud
  * del array: ''echo ${#array[@]}''
  * del primer elemento: ''echo ${#array}''
  * del tercero: ''echo ${#array[2]}''

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^Syntax ^Description ^
|**${#ARRAY[N]}** |Expands to the **length** of an individual array member at index **N** (**stringlength**) |
|**${#ARRAY[STRING]}** | Expands to the **length** of an individual associative array member at index **STRING** (**stringlength**) |
|**${#ARRAY[@]}**\\ **${#ARRAY[*]}**|Expands to the **number of elements** in **ARRAY** |
|**${!ARRAY[@]}**\\ **${!ARRAY[*]}**|Expands to the **indexes** in **ARRAY** since BASH 3.0|

</collapse>

== destrucción
The [[commands/builtin/unset | unset]] builtin command is used to destroy (unset) arrays or individual elements of arrays.

^Syntax ^Description ^
|''unset -v ARRAY''\\ ''unset -v ARRAY[@]''\\ ''unset -v ARRAY[*]'' |Destroys a complete array |
|''unset -v ARRAY[N]''|Destroys the array element at index ''N'' |
|''unset -v ARRAY[STRING]''|Destroys the array element of the associative array at index ''STRING'' |

usar siempre comillas para encerrar la variable para evitar problemas con las variables glob

== adición / eliminación / sustitución elementos
  * añadir elemento(s) a un array existente: ''array=("${array[@]}" "valor 3" "valor 4")''
  * eliminar un elemento n: ''unset array[n]''
    * existe forma de eliminar el índice o eliminar por patrón
  * eliminar un array: ''unset array''
  * cambiar string1 por string2: ''${array[@]/string1/string2}''
  * copiar un array: ''new_array=("${array[@]}")''
  * concatenar arrays: ''new_new_array=("${array[@]}" "${new_array[@]}")''

== cargar contenido de un fichero
  * ''array=(` cat file `)''

== ejemplos
=== quoted "*", quoted "@", unquoted
<sxh bash;title:Ejemplo Arrays en Bash>
#!/bin/bash

array=("first item" "second item" "third" "item")

echo "Number of items in original array: ${#array[*]}"
for ix in ${!array[*]}
do
    printf "   %s\n" "${array[$ix]}"
done
echo

arr=(${array[*]})
echo "After unquoted expansion: ${#arr[*]}"
for ix in ${!arr[*]}
do
    printf "   %s\n" "${arr[$ix]}"
done
echo

arr=("${array[*]}")
echo "After * quoted expansion: ${#arr[*]}"
for ix in ${!arr[*]}
do
    printf "   %s\n" "${arr[$ix]}"
done
echo

arr=("${array[@]}")
echo "After @ quoted expansion: ${#arr[@]}"
for ix in ${!arr[*]}
do
    printf "   %s\n" "${arr[$ix]}"
done
</sxh>
resultado:
<code txt>
Number of items in original array: 4
   first item
   second item
   third
   item

After unquoted expansion: 6
   first
   item
   second
   item
   third
   item

After * quoted expansion: 1
   first item second item third item

After @ quoted expansion: 4
   first item
   second item
   third
   item
</code>