Aquesta és una revisió antiga del document
arrays bash
/via: http://www.thegeekstuff.com/2010/06/bash-array-tutorial/
más información de interés (arrays indirection)
http://wiki.bash-hackers.org/syntax/arrays?rev=1534920675declaración y asignación
array=(valor0 'valor uno' 'valor dos')
array[0]='valor0' array[1]='valor uno' array[2]='valor dos'
inicialización durante declaración
declare -a array=(valor0 'valor uno' 'valor dos')
+ asignaciones
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[@]}")
recuperación
| 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[@]}« | Similar to 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}« | Similar to what this syntax does for the characters of a single string when doing 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. |
metada
| 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 |
destrucción
The unset builtin command is used to destroy (unset) arrays or individual elements of arrays.
| Syntax | Description |
|---|---|
unset -v ARRAYunset -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
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}
longitud
- del array:
echo ${#array[@]} - del primer elemento:
echo ${#array} - del tercero:
echo ${#array[2]}
adición / eliminación / sustitución elementos
- añadir elemento(s) a un array existente:
array=(«${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 `)
funky constructs
- todos los items del array:
${array[*]} - todos los índices del array:
${!array[*]} - número de items:
${#array[*]}
ejemplos
quoted "*", quoted "@", unquoted
#!/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
resultado:
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