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
When using bash arrays, you can remove an element in the following manner:
unset array[i] # where i is the array index
The problem with this is after the unset ${array[#]] is not truly valid. Yes
it does give you the number of active array elements, but not the actual array
depth. The index of the removed index in the array still exists. It simply has
been set inactive/null. For example:
declare -a array=( a b c d e )
unset array[2]
for ((i=0; i < ${#array[#]}; i++)) ; do
echo "$i: ${array[$i]}"
done
outputs the following:
0: a
1: b
2:
3: d
array[2] is still there but set to null or inactive
array[4] (e) does not show because ${#array[#]} is the number of active
array elements and not the true array element depth. This gets very messy very
quickly each time an element is unset
As an example consider the following code:
# array contains 0 or more strings
# remove looks for and removes a given string
remove () {
local str=$1
for (( i = 0 ; i < ${#array[#]}; i++ )) ; do
if [[ "${array[$i]}" == "$str" ]] ; then
unset array[$i]
return 0
fi
done
echo "$str: not registered"
return 0
}
This is only valid the first time remove is called. After that, valid
elements may be missed.
One fix for this is to added the following line after the unset:
unset array[$i]
+ array=( "${array[#]}" )
This re-initializes array with the element completely removed.
The problem, this feels kludgy.
So my questions are this:
1) is there a way of getting the true array element depth?
2) is there a way of detecting the end of an array when iterating through it?
3) is there another cleaner solution?
Understanding Why for ((i=0; i<${#array[#]}; i++)) is broken
There's no such thing as "true array element depth" in the sense that you're asking for here. Bash arrays aren't really arrays -- they're hash maps (numerically indexed for regular arrays, indexed by strings for bash 4.0's new "associative arrays"). As such, there's absolutely no reason for the keys to start from 0 -- you can have an array like the following: declare -a array=( [1000]="one thousand" [2000]="two thousand" [3000]="three thousand" ), and its length is exactly 3; there aren't a bunch of NUL/empty elements sitting between those items (looked up with keys 1000, 2000 and 3000, respectively).
Removing Elements From A Sparse Array Safely
Iterate over indices, if you want to remove by index. Whereas "${array[#]}" iterates over items in the array, "${!array[#]}" (note the !) iterates over by the indices by which those items can be looked up.
As you've observed, it's unsafe to assume that the indices range from 0 to the total number of items in an array, as bash arrays are allowed to be sparse -- but there's no reason to write your code to make that assumption in the first place.
for array_idx in "${!array[#]}"; do
unset "array[$array_idx]"
done
I have file.properties, where are keys and values defined:
key1=value1 value2 value3
key2=value4 value5 value6
key3=value7 value8 value9
I want to load lines from the file to array. I cannot use declare -A to create associative array because of bash 3.
In bash 4 my code is:
conf="./file.properties"
init() {
local configiration=$1
if [ -f "$conf" ]
then
while IFS='=' read -r key value
do
configuration[ ${key} ]=$value
done < "$conf"
fi}
declare -A configuration
init configuration
KEY="key value from file"
#KEY="key1" or KEY="key2" or KEY="key3"
SERVERS=${configuration[ $KEY ]}
I want to do the same job in bash 3.
conf="./file.properties"
init () {
key=()
value=()
if [ -f "$conf" ]
then
while IFS='=' read -r key value
do
key+=("$key")
value+=("$value")
done < "$conf"
fi}
init
KEY="key value from file"
#KEY="key1" or KEY="key2" or KEY="key3"
for ((i = 0; i < ${#key[#]}; i++))
do
if [ "${key[$i]}" == "$KEY" ];
then
echo "values: ${value[i]}"
fi
done
In both cases I get the same output, e.g.:
value1 value2 value3
Is my code for bash 3 correct or something has to be revised?
This looks correct to me, as you use an appropriate way to iterate through your arrays considering you just created them prior and know that the arrays' keys will be in 0,1,...,n-1 for your arrays of size n. The array+=(elements) operator always places elements into array starting at array's last index + 1.
The only case where I would iterate through an array differently is if it were not guaranteed that the indices are in [0,n). For example:
declare -ai roots=();
declare -i x y;
for ((x=0; x<4; roots[x*x]=x,++x)) do :; done;
for y in "${!roots[#]}"; do
printf 'sqrt(%d) = %d\n' $y ${roots[y]};
done;
By expanding the indices of roots using "${!roots[#]}"to iterate across it, we get the following output:
sqrt(0) = 0
sqrt(1) = 1
sqrt(4) = 2
sqrt(9) = 3
In cases like this, we have to avoid the arithmetic for loop to avoid something like the following from occurring:
$ for((i=0;i<${#roots[#]};++i)); do echo "${roots[i]}"; done;
0
1
The only change I would make is to use [[ instead of [ to perform string comparison, as it is a bash builtin which is safer and more efficient to use in general. Also, I believe you need either a newline or a ; before your } to close your init function.
This question already has answers here:
Remove an element from a Bash array
(19 answers)
Closed 6 years ago.
I have an array list in a bash script, and a variable var. I know that $var appears in ${list[#]}, but have no easy way of determining its index. I'd like to remove it from list.
This answer achieves something very close to what I need, except that list retains an empty element where $var once was. Note, e.g.:
$ list=(one two three)
$ var="two"
$ list=( "${list[#]/$var}" )
$ echo ${list[#]}
one three
$ echo ${#list[#]}
3
The same thing happens if I use delete=( "$var" ) and replace $var for $delete in the third line. Also, doing list=( "${list[#]/$var/}" ) makes no difference either.
(I'll note that, experimenting with the comment to that answer, I managed to match only whole words using list=( "${list[#]/%$var}" ), omitting the #.)
I also saw this answer proposing a nice trick to keep track of index and use unset, but that is unfeasible in my case. Finally, the same issue also appeared here, except that OP was satisfied with the result and probably didn't run into the problem empty elements create for me later on in my script, when I iterate through list. I tried to negate that problem by using expansion as follows, without any apparent effect:
for item in "${list[#]}"; do
if [ -n ${item:+'x'} ];then
...
fi
done
It's the same when I do [ ${#item} > 0 ], and I'm running out of ideas. Suggestions?
EDIT:
I have no understanding of why this happens, but #l0b0's comment made me notice something. Using the above preamble, I get:
$ for item in "${list[#]}"; do echo "Here!"; done
Here!
Here!
Here!
but:
$ for item in ${list[#]}; do echo "Here!"; done
Here!
Here!
I'm not sure I can omit the quotes in my script, though, as items are considerably more complicated there (file names and paths, both containing spaces and odd characters).
You can delete an element from existing array though the whole process isn't very straightforward and may appear like a hack.
#!/bin/bash
list=( "one" "two" "three" "four" "five" )
var1="two"
var2="four"
printf "%s\n" "Before:"
for (( i=0; i<${#list[#]}; i++ )); do
printf "%s = %s\n" "$i" "${list[i]}";
done
for (( i=0; i<${#list[#]}; i++ )); do
if [[ ${list[i]} == $var1 || ${list[i]} == $var2 ]]; then
list=( "${list[#]:0:$i}" "${list[#]:$((i + 1))}" )
i=$((i - 1))
fi
done
printf "\n%s\n" "After:"
for (( i=0; i<${#list[#]}; i++ )); do
printf "%s = %s\n" "$i" "${list[i]}";
done
This script outputs:
Before:
0 = one
1 = two
2 = three
3 = four
4 = five
After:
0 = one
1 = three
2 = five
Key part of the script is:
list=( "${list[#]:0:$i}" "${list[#]:$((i + 1))}" )
Here we re-construct your existing array by specifying the index and length to remove the element from array completely and re-order the indices.
If you want to delete the array element & shift the indices, you can use answer by l0b0 or JS웃.
However, if you don't want to shift the indices, you can use below script-let:
(Particularly useful for associative arrays)
$ list=(one two three)
$ delete_me=two
$ for i in ${!list[#]};do
if [ "${list[$i]}" == "$delete_me" ]; then
unset list[$i]
fi
done
$ for i in ${!list[#]};do echo "$i = ${list[$i]}"; done
0 = one
2 = three
If you want to shift the indices to make them continuous, re-construct the array as this:
$ list=("${list[#]}")
$ for i in ${!list[#]};do echo "$i = ${list[$i]}"; done
0 = one
1 = three
If you want to remove by value and shift the indexes I think you have to create a new array:
list=(one two three)
new_list=() # Not strictly necessary, but added for clarity
var="two"
for item in ${list[#]}
do
if [ "$item" != "$var" ]
then
new_list+=("$item")
fi
done
list=("${new_list[#]}")
unset new_list
Test:
$ echo "${list[#]}"
one three
$ echo "${#list[#]}"
2
I have a customized .profile that I use in ksh and below is a function that I created to skip back and forth from directories with overly complicated or long names.
As you can see, the pathnames are stored in an array (BOOKMARKS[]) to keep track of them and reference them at a later time. I want to be able to delete certain values from the array, using a case statement (or OPTARG if necessary) so that I can just type bmk -d # to remove the path at the associated index.
I have fiddled around with array +A and -A, but it just wound up screwing up my array (what is left in the commented out code may not be pretty...I didn't proofread it).
Any suggestions/tips on how to create that functionality? Thanks!
# To bookmark the current directory you are in for easy navigation back and forth from multiple non-aliased directories
# Use like 'bmk' (sets the current directory to a bookmark number) to go back to this directory, i.e. type 'bmk 3' (for the 3rd)
# To find out what directories are linked to which numbers, type 'bmk -l' (lowercase L)
# For every new directory bookmarked, the number will increase so the first time you run 'bmk' it will be 1 then 2,3,4...etc. for every consecutive run therea
fter
# TODO: finish -d (delete bookmark entry) function
make_bookmark()
{
if [[ $# -eq 0 ]]; then
BOOKMARKS[${COUNTER}]=${PWD}
(( COUNTER=COUNTER+1 ))
else
case $1 in
-l) NUM_OF_ELEMENTS=${#BOOKMARKS[*]}
while [[ ${COUNTER} -lt ${NUM_OF_ELEMENTS} ]]
do
(( ACTUAL_NUM=i+1 ))
echo ${ACTUAL_NUM}":"${BOOKMARKS[${i}]}
(( COUNTER=COUNTER+1 ))
done
break ;;
#-d) ACTUAL_NUM=$2
#(( REMOVE=${ACTUAL_NUM}-1 ))
#echo "Removing path ${BOOKMARKS[${REMOVE}]} from 'bmk'..."
#NUM_OF_ELEMENTS=${#BOOKMARKS[*]}
#while [[ ${NUM_OF_ELEMENTS} -gt 0 ]]
#do
#if [[ ${NUM_OF_ELEMENTS} -ne ${ACTUAL_NUM} ]]; then
# TEMP_ARR=$(echo "${BOOKMARKS[*]}")
# (( NUM_OF_ELEMENTS=${NUM_OF_ELEMENTS}-1 ))
#fi
#echo $TEMP_ARR
#done
#break
#for VALUE in ${TEMP_ARR}
#do
# set +A BOOKMARK ${TEMP_ARR}
#done
#echo ${BOOKMARK[*]}
#break ;;
*) (( INDEX=$1-1 ))
cd ${BOOKMARKS[${INDEX}]}
break ;;
esac
fi
}
Arrays in the Korn shell (and Bash and others) are sparse, so if you use unset to delete members of the array, you won't be able to use the size of the array as an index to the last member and other limitations.
Here are some useful snippets (the second for loop is something you might be able to put to use right away):
array=(1 2 3)
unset array[2]
echo ${array[2]} # null
indices=(${!array[#]}) # create an array of the indices of "array"
size=${#indices[#]} # the size of "array" is the number of indices into it
size=${#array[#]} # same
echo ${array[#]: -1} # you can use slices to get array elements, -1 is the last one, etc.
for element in ${array[#]}; do # iterate over the array without an index
for index in ${indices[#]} # iterate over the array WITH an index
do
echo "Index: ${index}, Element: ${array[index]}"
done
for index in ${!array[#]} # iterate over the array WITH an index, directly
That last one can eliminate the need for a counter.
Here are a couple more handy techniques:
array+=("new element") # append a new element without referring to an index
((counter++)) # shorter than ((counter=counter+1)) or ((counter+=1))
if [[ $var == 3 ]] # you can use the more "natural" comparison operators inside double square brackets
while [[ $var < 11 ]] # another example
echo ${array[${index}-1] # math inside an array subscript
This all assumes ksh93, some things may not work in earlier versions.
you can use unset. eg to delete array element 1
unset array[0]
to delete entire array
unset array
A few caveats regarding the previous answer:
First: I see this error all the time. When you provide an array element to "unset", you have to quote it. Consider:
$ echo foo > ./a2
$ ls a[2]
a2
$ a2="Do not delete this"
$ a=(this is not an array)
$ unset -v a[2]
$ echo "a2=${a2-UNSET}, a[]=${a[#]}"
a2=UNSET a[]=this is not an array
What happened? Globbing. You obviously wanted to delete element 2 of a[], but shell syntax being what it is, the shell first checked the current directory for a file that matched the glob pattern "a[2]". If it finds a match, it replaces the glob pattern with that filename, and you wind up making a decision about which variable to delete based on what files exist in your current directory.
This is profoundly stupid. But it's not something anyone has bothered to fix, apparently, and the error turns up in all kinds of documentation and example code from the last 3 decades.
Next is a related problem: it's easy to insert elements in your associative array with any key you like. But it's harder to remove these elements:
typeset -A assoc
key="foo] bar"
assoc[$key]=3 #No problem!
unset -v "assoc[$key]" #Problem!
In bash you can do this:
unset -v "assoc[\$key]"
In Korn Shell, you have to do this:
unset -v "assoc[foo\]\ bar]"
So it gets a bit more complicated in the case where your keys contain syntax characters.