I have a text file with the following:
Paige
Buckley
Govan
Mayer
King
Harrison
Atkins
Reinhardt
Wilson
Vaughan
Sergovia
Tarrega
My goal is to create an array for each set of names. Then Iterate through the first array of values then move on to the second array of values and lastly the third array. Each set is separated by a new line in the text file. Help with code or logic is much appreciated!
so far I have the following. i am unsure of the logic moving forward when i reach a line break. My research here also suggests that i can use readarray -d.
#!/bin/bash
my_array=()
while IFS= read -r line || [[ "$line" ]]; do
if [[ $line -eq "" ]];
.
.
.
arr+=("$line") # i know this adds the value to the array
done < "$1"
printf '%s\n' "${my_array[#]}"
desired output:
array1 = (Paige Buckley6 Govan Mayer King)
array2 = (Harrison Atkins Reinhardt Wilson)
array3 = (Vaughan Sergovia Terrega)
#then loop through the each array one after the other.
Bash has no array-of-arrays. So you have to represent it in an other way.
You could leave the newlines and have an array of newline separated elements:
array=()
elem=""
while IFS= read -r line; do
if [[ "$line" != "" ]]; then
elem+="${elem:+$'\n'}$line" # accumulate lines in elem
else
array+=("$elem") # flush elem as array element
elem=""
fi
done
if [[ -n "$elem" ]]; then
array+=("$elem") # flush the last elem
fi
# iterate over array
for ((i=0;i<${#array[#]};++i)); do
# each array element is newline separated items
readarray -t elem <<<"${array[i]}"
printf 'array%d = (%s)\n' "$i" "${elem[*]}"
done
You could simplify the loop with some unique character and a sed for example like:
readarray -d '#' -t array < <(sed -z 's/\n\n/#/g' file)
But overall, this awk generates same output:
awk -v RS= -v FS='\n' '{
printf "array%d = (", NR;
for (i=1;i<=NF;++i) printf "%s%s", $i, i==NF?"":" ";
printf ")\n"
}'
Using nameref :
#!/usr/bin/env bash
declare -a array1 array2 array3
declare -n array=array$((n=1))
while IFS= read -r line; do
test "$line" = "" && declare -n array=array$((n=n+1)) || array+=("$line")
done < "$1"
declare -p array1 array2 array3
Called with :
bash test.sh data
# result
declare -a array1=([0]="Paige" [1]="Buckley" [2]="Govan" [3]="Mayer" [4]="King")
declare -a array2=([0]="Harrison" [1]="Atkins" [2]="Reinhardt" [3]="Wilson")
declare -a array3=([0]="Vaughan" [1]="Sergovia" [2]="Tarrega")
Assumptions:
blank links are truly blank (ie, no need to worry about any white space on said lines)
could have consecutive blank lines
names could have embedded white space
the number of groups could vary and won't always be 3 (as with the sample data provided in the question)
OP is open to using a (simulated) 2-dimensional array as opposed to a (variable) number of 1-dimensional arrays
My data file:
$ cat names.dat
<<< leading blank lines
Paige
Buckley
Govan
Mayer
King Kong
<<< consecutive blank lines
Harrison
Atkins
Reinhardt
Wilson
Larry
Moe
Curly
Shemp
Vaughan
Sergovia
Tarrega
<<< trailing blank lines
One idea that uses a couple arrays:
array #1: associative array - the previously mentioned (simulated) 2-dimensional array with the index - [x,y] - where x is a unique identifier for a group of names and y is a unique identifier for a name within a group
array #2: 1-dimensional array to keep track of max(y) for each group x
Loading the arrays:
unset names max_y # make sure array names are not already in use
declare -A names # declare associative array
x=1 # init group counter
y=0 # init name counter
max_y=() # initialize the max(y) array
inc= # clear increment flag
while read -r name
do
if [[ "${name}" = '' ]] # if we found a blank line ...
then
[[ "${y}" -eq 0 ]] && # if this is a leading blank line then ...
continue # ignore and skip to the next line
inc=y # set flag to increment 'x'
else
[[ "${inc}" = 'y' ]] && # if increment flag is set ...
max_y[${x}]="${y}" && # make note of max(y) for this 'x'
((x++)) && # increment 'x' (group counter)
y=0 && # reset 'y'
inc= # clear increment flag
((y++)) # increment 'y' (name counter)
names[${x},${y}]="${name}" # save the name
fi
done < names.dat
max_y[${x}]="${y}" # make note of the last max(y) value
Contents of the array:
$ typeset -p names
declare -A names=([1,5]="King Kong" [1,4]="Mayer" [1,1]="Paige" [1,3]="Govan" [1,2]="Buckley" [3,4]="Shemp" [3,3]="Curly" [3,2]="Moe" [3,1]="Larry" [2,4]="Wilson" [2,2]="Atkins" [2,3]="Reinhardt" [2,1]="Harrison" [4,1]="Vaughan" [4,2]="Sergovia" [4,3]="Tarrega" )
$ for (( i=1; i<=${x}; i++ ))
do
for (( j=1; j<=${max_y[${i}]}; j++ ))
do
echo "names[${i},${j}] : ${names[${i},${j}]}"
done
echo ""
done
names[1,1] : Paige
names[1,2] : Buckley
names[1,3] : Govan
names[1,4] : Mayer
names[1,5] : King Kong
names[2,1] : Harrison
names[2,2] : Atkins
names[2,3] : Reinhardt
names[2,4] : Wilson
names[3,1] : Larry
names[3,2] : Moe
names[3,3] : Curly
names[3,4] : Shemp
names[4,1] : Vaughan
names[4,2] : Sergovia
names[4,3] : Tarrega
can you help me getting rid off the nested for loop?
Array may change all the time, as of right now i need to add/remove for loops. Is it possible with pure bash to replace nested for loops with more elegant solution?
#!/bin/bash
i=0
array=(A B C)
places=3
word1=word1
word2=word2
arrC=${#array[*]}
while [ $i -lt $((arrC**places)) ]; do
for a in ${!array[*]}; do
for b in ${!array[*]}; do
for c in ${!array[*]}; do
echo "[$i] ${array[$a]}${word1}${array[$b]}${word2}${array[$c]}"
i=$((i + 1))
done
done
done
done
I've made ABC array for simplicity. Here is more of a real example for an array:
array=(I i L l | \ / 1 !)
Use recursion.
#! /bin/bash
array=(A B C)
words=(word1 word2)
combine () {
local depth=$1
local prefix=${2# }
shift 2
if ((depth == ${#array[#]})) ; then
echo "$prefix"
return
fi
local i
for (( i=1; i<=$#; ++i )) ; do
combine $((depth+1)) "$prefix${!i}${words[depth]}" "${array[#]}"
done
}
combine 0 "" "${array[#]}"
Looking at an awk solution that uses a recursive function to allow for a dynamic number of for loops.
But first a couple mods to the input parameters (to make it easier to pass info into awk); we'll replace bash level arrays with simple variables (using a : as a delimiter for this exercise):
array_s="A:B:C:D"
words_s="${word1}:${word2}"
One awk idea:
awk -v places="${places}" -v words_s="${words_s}" -v array_s="${array_s}" '
function print_place(place,outstring, j, sfx) { # define but do not pass "j" and "sfx";
# this designates these as local variables
if ( place > places ) # if we haveve exceeded the number of places ...
{ i++ # increment our counter
printf "%s\n", outstring # print our string to stdout
return # and exit this invocation of the function
}
if ( i > total ) return # if we have exceeded total number of outputs
# then exit this invocation of the function
sfx="" # default suffix is "" unless we
if ( place < places ) sfx=words[place] # have not reached the max number of places
for ( j=1 ; j<=n ; j++ ) # loop through arr[] entries
print_place(place+1,outstring arr[j] sfx) # recursive function call for place+1; also pass along
# our growing string
}
BEGIN { n=split(array_s,arr,":") # parse "array_s" into awk array "arr[]"
m=split(words_s,words,":") # parse "words_s" into awak array "words[]"
total=n**places # calculate total number of strings to print
i=0 # init counter
print_place(1,"") # call function
}
'
Some sample runs:
places=3
array_s="A:B:C"
words_s="word1:word2"
awk ...
Aword1Aword2A
Aword1Aword2B
Aword1Aword2C
Aword1Bword2A
Aword1Bword2B
Aword1Bword2C
...snip...
Cword1Cword2A
Cword1Cword2B
Cword1Cword2C # 27 lines of output
##############
places=2
array_s="A:B:C:D"
words_s="word1:word2"
awk ...
Aword1A
Aword1B
Aword1C
Aword1D
Bword1A
Bword1B
Bword1C
Bword1D
Cword1A
Cword1B
Cword1C
Cword1D
Dword1A
Dword1B
Dword1C
Dword1D # 16 lines of output
##############
places=4
array_s="A:B:C:D"
words_s="word1:word2:word3"
awk ...
Aword1Aword2Aword3A
Aword1Aword2Aword3B
Aword1Aword2Aword3C
Aword1Aword2Aword3D
Aword1Aword2Bword3A
Aword1Aword2Bword3B
Aword1Aword2Bword3C
Aword1Aword2Bword3D
Aword1Aword2Cword3A
Aword1Aword2Cword3B
...snip...
Dword1Dword2Cword3D
Dword1Dword2Dword3A
Dword1Dword2Dword3B
Dword1Dword2Dword3C
Dword1Dword2Dword3D # 256 lines of output
I need to remove an element from an array in bash shell.
Generally I'd simply do:
array=("${(#)array:#<element to remove>}")
Unfortunately the element I want to remove is a variable so I can't use the previous command.
Down here an example:
array+=(pluto)
array+=(pippo)
delete=(pluto)
array( ${array[#]/$delete} ) -> but clearly doesn't work because of {}
Any idea?
The following works as you would like in bash and zsh:
$ array=(pluto pippo)
$ delete=pluto
$ echo ${array[#]/$delete}
pippo
$ array=( "${array[#]/$delete}" ) #Quotes when working with strings
If need to delete more than one element:
...
$ delete=(pluto pippo)
for del in ${delete[#]}
do
array=("${array[#]/$del}") #Quotes when working with strings
done
Caveat
This technique actually removes prefixes matching $delete from the elements, not necessarily whole elements.
Update
To really remove an exact item, you need to walk through the array, comparing the target to each element, and using unset to delete an exact match.
array=(pluto pippo bob)
delete=(pippo)
for target in "${delete[#]}"; do
for i in "${!array[#]}"; do
if [[ ${array[i]} = $target ]]; then
unset 'array[i]'
fi
done
done
Note that if you do this, and one or more elements is removed, the indices will no longer be a continuous sequence of integers.
$ declare -p array
declare -a array=([0]="pluto" [2]="bob")
The simple fact is, arrays were not designed for use as mutable data structures. They are primarily used for storing lists of items in a single variable without needing to waste a character as a delimiter (e.g., to store a list of strings which can contain whitespace).
If gaps are a problem, then you need to rebuild the array to fill the gaps:
for i in "${!array[#]}"; do
new_array+=( "${array[i]}" )
done
array=("${new_array[#]}")
unset new_array
You could build up a new array without the undesired element, then assign it back to the old array. This works in bash:
array=(pluto pippo)
new_array=()
for value in "${array[#]}"
do
[[ $value != pluto ]] && new_array+=($value)
done
array=("${new_array[#]}")
unset new_array
This yields:
echo "${array[#]}"
pippo
This is the most direct way to unset a value if you know it's position.
$ array=(one two three)
$ echo ${#array[#]}
3
$ unset 'array[1]'
$ echo ${array[#]}
one three
$ echo ${#array[#]}
2
This answer is specific to the case of deleting multiple values from large arrays, where performance is important.
The most voted solutions are (1) pattern substitution on an array, or (2) iterating over the array elements. The first is fast, but can only deal with elements that have distinct prefix, the second has O(n*k), n=array size, k=elements to remove. Associative array are relative new feature, and might not have been common when the question was originally posted.
For the exact match case, with large n and k, possible to improve performance from O(nk) to O(n+klog(k)). In practice, O(n) assuming k much lower than n. Most of the speed up is based on using associative array to identify items to be removed.
Performance (n-array size, k-values to delete). Performance measure seconds of user time
N K New(seconds) Current(seconds) Speedup
1000 10 0.005 0.033 6X
10000 10 0.070 0.348 5X
10000 20 0.070 0.656 9X
10000 1 0.043 0.050 -7%
As expected, the current solution is linear to N*K, and the fast solution is practically linear to K, with much lower constant. The fast solution is slightly slower vs the current solution when k=1, due to additional setup.
The 'Fast' solution: array=list of input, delete=list of values to remove.
declare -A delk
for del in "${delete[#]}" ; do delk[$del]=1 ; done
# Tag items to remove, based on
for k in "${!array[#]}" ; do
[ "${delk[${array[$k]}]-}" ] && unset 'array[k]'
done
# Compaction
array=("${array[#]}")
Benchmarked against current solution, from the most-voted answer.
for target in "${delete[#]}"; do
for i in "${!array[#]}"; do
if [[ ${array[i]} = $target ]]; then
unset 'array[i]'
fi
done
done
array=("${array[#]}")
Here's a one-line solution with mapfile:
$ mapfile -d $'\0' -t arr < <(printf '%s\0' "${arr[#]}" | grep -Pzv "<regexp>")
Example:
$ arr=("Adam" "Bob" "Claire"$'\n'"Smith" "David" "Eve" "Fred")
$ echo "Size: ${#arr[*]} Contents: ${arr[*]}"
Size: 6 Contents: Adam Bob Claire
Smith David Eve Fred
$ mapfile -d $'\0' -t arr < <(printf '%s\0' "${arr[#]}" | grep -Pzv "^Claire\nSmith$")
$ echo "Size: ${#arr[*]} Contents: ${arr[*]}"
Size: 5 Contents: Adam Bob David Eve Fred
This method allows for great flexibility by modifying/exchanging the grep command and doesn't leave any empty strings in the array.
Partial answer only
To delete the first item in the array
unset 'array[0]'
To delete the last item in the array
unset 'array[-1]'
To expand on the above answers, the following can be used to remove multiple elements from an array, without partial matching:
ARRAY=(one two onetwo three four threefour "one six")
TO_REMOVE=(one four)
TEMP_ARRAY=()
for pkg in "${ARRAY[#]}"; do
for remove in "${TO_REMOVE[#]}"; do
KEEP=true
if [[ ${pkg} == ${remove} ]]; then
KEEP=false
break
fi
done
if ${KEEP}; then
TEMP_ARRAY+=(${pkg})
fi
done
ARRAY=("${TEMP_ARRAY[#]}")
unset TEMP_ARRAY
This will result in an array containing:
(two onetwo three threefour "one six")
Here's a (probably very bash-specific) little function involving bash variable indirection and unset; it's a general solution that does not involve text substitution or discarding empty elements and has no problems with quoting/whitespace etc.
delete_ary_elmt() {
local word=$1 # the element to search for & delete
local aryref="$2[#]" # a necessary step since '${!$2[#]}' is a syntax error
local arycopy=("${!aryref}") # create a copy of the input array
local status=1
for (( i = ${#arycopy[#]} - 1; i >= 0; i-- )); do # iterate over indices backwards
elmt=${arycopy[$i]}
[[ $elmt == $word ]] && unset "$2[$i]" && status=0 # unset matching elmts in orig. ary
done
return $status # return 0 if something was deleted; 1 if not
}
array=(a 0 0 b 0 0 0 c 0 d e 0 0 0)
delete_ary_elmt 0 array
for e in "${array[#]}"; do
echo "$e"
done
# prints "a" "b" "c" "d" in lines
Use it like delete_ary_elmt ELEMENT ARRAYNAME without any $ sigil. Switch the == $word for == $word* for prefix matches; use ${elmt,,} == ${word,,} for case-insensitive matches; etc., whatever bash [[ supports.
It works by determining the indices of the input array and iterating over them backwards (so deleting elements doesn't screw up iteration order). To get the indices you need to access the input array by name, which can be done via bash variable indirection x=1; varname=x; echo ${!varname} # prints "1".
You can't access arrays by name like aryname=a; echo "${$aryname[#]}, this gives you an error. You can't do aryname=a; echo "${!aryname[#]}", this gives you the indices of the variable aryname (although it is not an array). What DOES work is aryref="a[#]"; echo "${!aryref}", which will print the elements of the array a, preserving shell-word quoting and whitespace exactly like echo "${a[#]}". But this only works for printing the elements of an array, not for printing its length or indices (aryref="!a[#]" or aryref="#a[#]" or "${!!aryref}" or "${#!aryref}", they all fail).
So I copy the original array by its name via bash indirection and get the indices from the copy. To iterate over the indices in reverse I use a C-style for loop. I could also do it by accessing the indices via ${!arycopy[#]} and reversing them with tac, which is a cat that turns around the input line order.
A function solution without variable indirection would probably have to involve eval, which may or may not be safe to use in that situation (I can't tell).
Using unset
To remove an element at particular index, we can use unset and then do copy to another array. Only just unset is not required in this case. Because unset does not remove the element it just sets null string to the particular index in array.
declare -a arr=('aa' 'bb' 'cc' 'dd' 'ee')
unset 'arr[1]'
declare -a arr2=()
i=0
for element in "${arr[#]}"
do
arr2[$i]=$element
((++i))
done
echo "${arr[#]}"
echo "1st val is ${arr[1]}, 2nd val is ${arr[2]}"
echo "${arr2[#]}"
echo "1st val is ${arr2[1]}, 2nd val is ${arr2[2]}"
Output is
aa cc dd ee
1st val is , 2nd val is cc
aa cc dd ee
1st val is cc, 2nd val is dd
Using :<idx>
We can remove some set of elements using :<idx> also. For example if we want to remove 1st element we can use :1 as mentioned below.
declare -a arr=('aa' 'bb' 'cc' 'dd' 'ee')
arr2=("${arr[#]:1}")
echo "${arr2[#]}"
echo "1st val is ${arr2[1]}, 2nd val is ${arr2[2]}"
Output is
bb cc dd ee
1st val is cc, 2nd val is dd
http://wiki.bash-hackers.org/syntax/pe#substring_removal
${PARAMETER#PATTERN} # remove from beginning
${PARAMETER##PATTERN} # remove from the beginning, greedy match
${PARAMETER%PATTERN} # remove from the end
${PARAMETER%%PATTERN} # remove from the end, greedy match
In order to do a full remove element, you have to do an unset command with an if statement. If you don't care about removing prefixes from other variables or about supporting whitespace in the array, then you can just drop the quotes and forget about for loops.
See example below for a few different ways to clean up an array.
options=("foo" "bar" "foo" "foobar" "foo bar" "bars" "bar")
# remove bar from the start of each element
options=("${options[#]/#"bar"}")
# options=("foo" "" "foo" "foobar" "foo bar" "s" "")
# remove the complete string "foo" in a for loop
count=${#options[#]}
for ((i = 0; i < count; i++)); do
if [ "${options[i]}" = "foo" ] ; then
unset 'options[i]'
fi
done
# options=( "" "foobar" "foo bar" "s" "")
# remove empty options
# note the count variable can't be recalculated easily on a sparse array
for ((i = 0; i < count; i++)); do
# echo "Element $i: '${options[i]}'"
if [ -z "${options[i]}" ] ; then
unset 'options[i]'
fi
done
# options=("foobar" "foo bar" "s")
# list them with select
echo "Choose an option:"
PS3='Option? '
select i in "${options[#]}" Quit
do
case $i in
Quit) break ;;
*) echo "You selected \"$i\"" ;;
esac
done
Output
Choose an option:
1) foobar
2) foo bar
3) s
4) Quit
Option?
Hope that helps.
There is also this syntax, e.g. if you want to delete the 2nd element :
array=("${array[#]:0:1}" "${array[#]:2}")
which is in fact the concatenation of 2 tabs. The first from the index 0 to the index 1 (exclusive) and the 2nd from the index 2 to the end.
POSIX shell script does not have arrays.
So most probably you are using a specific dialect such as bash, korn shells or zsh.
Therefore, your question as of now cannot be answered.
Maybe this works for you:
unset array[$delete]
What I do is:
array="$(echo $array | tr ' ' '\n' | sed "/itemtodelete/d")"
BAM, that item is removed.
This is a quick-and-dirty solution that will work in simple cases but will break if (a) there are regex special characters in $delete, or (b) there are any spaces at all in any items. Starting with:
array+=(pluto)
array+=(pippo)
delete=(pluto)
Delete all entries exactly matching $delete:
array=(`echo $array | fmt -1 | grep -v "^${delete}$" | fmt -999999`)
resulting in
echo $array -> pippo, and making sure it's an array:
echo $array[1] -> pippo
fmt is a little obscure: fmt -1 wraps at the first column (to put each item on its own line. That's where the problem arises with items in spaces.) fmt -999999 unwraps it back to one line, putting back the spaces between items. There are other ways to do that, such as xargs.
Addendum: If you want to delete just the first match, use sed, as described here:
array=(`echo $array | fmt -1 | sed "0,/^${delete}$/{//d;}" | fmt -999999`)
Actually, I just noticed that the shell syntax somewhat has a behavior built-in that allows for easy reconstruction of the array when, as posed in the question, an item should be removed.
# let's set up an array of items to consume:
x=()
for (( i=0; i<10; i++ )); do
x+=("$i")
done
# here, we consume that array:
while (( ${#x[#]} )); do
i=$(( $RANDOM % ${#x[#]} ))
echo "${x[i]} / ${x[#]}"
x=("${x[#]:0:i}" "${x[#]:i+1}")
done
Notice how we constructed the array using bash's x+=() syntax?
You could actually add more than one item with that, the content of a whole other array at once.
In ZSH this is dead easy (note this uses more bash compatible syntax than necessary where possible for ease of understanding):
# I always include an edge case to make sure each element
# is not being word split.
start=(one two three 'four 4' five)
work=(${(#)start})
idx=2
val=${work[idx]}
# How to remove a single element easily.
# Also works for associative arrays (at least in zsh)
work[$idx]=()
echo "Array size went down by one: "
[[ $#work -eq $(($#start - 1)) ]] && echo "OK"
echo "Array item "$val" is now gone: "
[[ -z ${work[(r)$val]} ]] && echo OK
echo "Array contents are as expected: "
wanted=("${start[#]:0:1}" "${start[#]:2}")
[[ "${(j.:.)wanted[#]}" == "${(j.:.)work[#]}" ]] && echo "OK"
echo "-- array contents: start --"
print -l -r -- "-- $#start elements" ${(#)start}
echo "-- array contents: work --"
print -l -r -- "-- $#work elements" "${work[#]}"
Results:
Array size went down by one:
OK
Array item two is now gone:
OK
Array contents are as expected:
OK
-- array contents: start --
-- 5 elements
one
two
three
four 4
five
-- array contents: work --
-- 4 elements
one
three
four 4
five
To avoid conflicts with array index using unset - see https://stackoverflow.com/a/49626928/3223785 and https://stackoverflow.com/a/47798640/3223785 for more information - reassign the array to itself: ARRAY_VAR=(${ARRAY_VAR[#]}).
#!/bin/bash
ARRAY_VAR=(0 1 2 3 4 5 6 7 8 9)
unset ARRAY_VAR[5]
unset ARRAY_VAR[4]
ARRAY_VAR=(${ARRAY_VAR[#]})
echo ${ARRAY_VAR[#]}
A_LENGTH=${#ARRAY_VAR[*]}
for (( i=0; i<=$(( $A_LENGTH -1 )); i++ )) ; do
echo ""
echo "INDEX - $i"
echo "VALUE - ${ARRAY_VAR[$i]}"
done
exit 0
[Ref.: https://tecadmin.net/working-with-array-bash-script/ ]
How about something like:
array=(one two three)
array_t=" ${array[#]} "
delete=one
array=(${array_t// $delete / })
unset array_t
#/bin/bash
echo "# define array with six elements"
arr=(zero one two three 'four 4' five)
echo "# unset by index: 0"
unset -v 'arr[0]'
for i in ${!arr[*]}; do echo "arr[$i]=${arr[$i]}"; done
arr_delete_by_content() { # value to delete
for i in ${!arr[*]}; do
[ "${arr[$i]}" = "$1" ] && unset -v 'arr[$i]'
done
}
echo "# unset in global variable where value: three"
arr_delete_by_content three
for i in ${!arr[*]}; do echo "arr[$i]=${arr[$i]}"; done
echo "# rearrange indices"
arr=( "${arr[#]}" )
for i in ${!arr[*]}; do echo "arr[$i]=${arr[$i]}"; done
delete_value() { # value arrayelements..., returns array decl.
local e val=$1; new=(); shift
for e in "${#}"; do [ "$val" != "$e" ] && new+=("$e"); done
declare -p new|sed 's,^[^=]*=,,'
}
echo "# new array without value: two"
declare -a arr="$(delete_value two "${arr[#]}")"
for i in ${!arr[*]}; do echo "arr[$i]=${arr[$i]}"; done
delete_values() { # arraydecl values..., returns array decl. (keeps indices)
declare -a arr="$1"; local i v; shift
for v in "${#}"; do
for i in ${!arr[*]}; do
[ "$v" = "${arr[$i]}" ] && unset -v 'arr[$i]'
done
done
declare -p arr|sed 's,^[^=]*=,,'
}
echo "# new array without values: one five (keep indices)"
declare -a arr="$(delete_values "$(declare -p arr|sed 's,^[^=]*=,,')" one five)"
for i in ${!arr[*]}; do echo "arr[$i]=${arr[$i]}"; done
# new array without multiple values and rearranged indices is left to the reader
I am storing a file list in an array . What I'd like to do is loop through a process that will read N elements of an array and delete all the elements it just read. The Exception is the last iteration , when you come to the last iteration of the loop - whatever remains in the array - just split that out .
th=$1
ar=('f1' 'f2' 'f3' 'f4' 'f5' 'f6')
for ((i=1; i<=$th; i++)); do
<stuff>
if [ "$i" -eq "$th" ]
then
# if its the last iteration of the loop.Whatever remains in the array - spit that out
echo " `echo ${ar[*]}`" >> somefile
# it its anything short of the last iteration.Read N elements of the array at a time
# and then delete them
else
echo " `echo ${ar[*]:0:$N}` " >> somefile
for ((x=0; x<=$N; x++)) ; do
unset ar[$x]
done
fi
The results are very erratic. Even when I use this approach and test if separately
for ((x=0; x<=$N; x++)) ; do
unset ar[$x]
done
It will delete the WHOLE array EXCEPT the $Nth element
I am new to arrays in shell. Any help is gladly appreciated
Try the following:
#! /bin/bash
th=3
N=2
ar=('f1 f' 'f2' 'f3' 'f4 x' 'f5' 'f6' 'f7')
for ((i=0; i<$th; i++)); do
if (( $i == $(($th - 1)) )) ; then
echo "${ar[*]}"
else
echo "${ar[*]:0:$N}"
ar=( "${ar[#]:$N}" )
fi
done
Output:
f1 f f2
f3 f4 x
f5 f6 f7
Note:
Arrays in bash are zero based.
Indices are not adjusted after unset ar[$x], therefore it would be easier to reconstruct the array as ar=( "${ar[#]:$N}" ) to force new indices to start at zero..
Update:
Or you could avoid the reconstruction of the array using:
#! /bin/bash
th=3
N=2
ar=('f1 f' 'f2' 'f3' 'f4 x' 'f5' 'f6' 'f7')
for ((i=0; i<$th; i++)); do
if (( $i == $(($th - 1)) )) ; then
echo "${ar[*]:$(($i * $N))}"
else
echo "${ar[*]:$(($i * $N)):$N}"
fi
done