I get the following output:
Pushkin - 100500
Gogol - 23
Dostoyevsky - 9999
Which is the result of the following script:
for k in "${!authors[@]}"
do
echo $k ' - ' ${authors["$k"]}
done
All I want is to get the output like this:
Pushkin - 100500
Dostoyevsky - 9999
Gogol - 23
which means that the keys in associative array should be sorted by value. Is there an easy method to do so?
You can easily sort your output, in descending numerical order of the 3rd field:
for k in "${!authors[@]}"
do
echo $k ' - ' ${authors["$k"]}
done |
sort -rn -k3
See sort(1) for more about the sort command. This just sorts output lines; I don't know of any way to sort an array directly in bash.
I also can't see how the above can give you names ("Pushkin" et al.) as array keys. In bash, array keys are always integers.
declare -A authors.
Alternatively you can sort the indexes and use the sorted list of indexes to loop through the array:
authors_indexes=( ${!authors[@]} )
IFS=$'\n' authors_sorted=( $(echo -e "${authors_indexes[@]/%/\n}" | sed -r -e 's/^ *//' -e '/^$/d' | sort) )
for k in "${authors_sorted[@]}"; do
echo $k ' - ' ${authors["$k"]}
done
echo -e. Consider printf '%s\n' "${authors_indexes[@]}" to expand an array into multiple lines in a way that doesn't depend on violations of POSIX sh (not just extensions, but actual violations: Any argument other than -n is required to print its text, unless it contains backslashes or -n is present, in which case behavior is entirely implementation-defined). Or printf '%s\0' "${array[@]}" to expand the array as NUL-delimit strings, thus in a manner that works even if you have literal newlines in your keys (which are legal).
oIFS="$IFS" IFS=$'\n' authors_sorted=( $( printf '%s\n' "${!authors[@]}" | sort ) ) IFS="$oIFS"Extending the answer from @AndrewSchulman, using -rn as a global sort option reverses all columns. In this example, authors with the same associative array value will be output by reverse order of name.
For example
declare -A authors
authors=( [Pushkin]=10050 [Gogol]=23 [Dostoyevsky]=9999 [Tolstoy]=23 )
for k in "${!authors[@]}"
do
echo $k ' - ' ${authors["$k"]}
done | sort -rn -k3
will output
Pushkin - 10050 Dostoyevsky - 9999 Tolstoy - 23 Gogol - 23Options for sorting specific columns can be provided after the column specifier. i.e.
sort -k3rn
Note that keys can be specified as spans. Here -k3 happens to be fine because it is the final span, but to use only column 3 explicitly (in case further columns were added), it should be specified as -k3,3,
Similarly to sort by column three in descending order, and then column one in ascending order (which is probably what is desired in this example):
declare -A authors
authors=( [Pushkin]=10050 [Gogol]=23 [Dostoyevsky]=9999 [Tolstoy]=23 )
for k in "${!authors[@]}"
do
echo $k ' - ' ${authors["$k"]}
done | sort -k3,3rn -k1,1
will output
Pushkin - 10050 Dostoyevsky - 9999 Gogol - 23 Tolstoy - 23
The best way to sort a bash associative array by VALUE is to NOT sort it.
Instead, get the list of VALUE:::KEYS, sort that list into a new KEY LIST, and iterate through the list.
declare -A ADDR
ADDR[192.168.1.3]="host3"
ADDR[192.168.1.1]="host1"
ADDR[192.168.1.2]="host2"
KEYS=$(
for KEY in ${!ADDR[@]}; do
echo "${ADDR[$KEY]}:::$KEY"
done | sort | awk -F::: '{print $2}'
)
for KEY in $KEYS; do
VAL=${ADDR[$KEY]}
echo "KEY=[$KEY] VAL=[$VAL]"
done
output:
KEY=[192.168.1.1] VAL=[host1]
KEY=[192.168.1.2] VAL=[host2]
KEY=[192.168.1.3] VAL=[host3]
Do something with unsorted keys:
for key in ${!Map[@]}; do
echo $key
done
Do something with sorted keys:
for key in $(for x in ${!Map[@]}; do echo $x; done | sort); do
echo $key
done
Store sorted keys as array:
Keys=($(for x in ${!Map[@]}; do echo $x; done | sort))
echo with a space in an inline nested loop can be problematic; My solution was to use printf and not use a space: for kvp in $(for key in ${!Map[@]}; do printf '%s:%s\n' "$key" "${Map[$key]}"; done | sort -t: -rn -k2); do echo "$kvp"; done
"${Map[@]}" and echo "$x".If you can assume the value is always a number (no spaces), but want to allow for the possibility of spaces in the key:
for k in "${!authors[@]}"; do
echo "${authors["$k"]} ${k}"
done | sort -rn | while read number author; do
echo "${author} - ${number}"
done
Example:
$ declare -A authors
$ authors=(['Shakespeare']=1 ['Kant']=2 ['Von Neumann']=3 ['Von Auersperg']=4)
$ for k in "${!authors[@]}"; do echo "${authors["$k"]} ${k}"; done | sort -rn | while read number author; do echo "${author} - ${number}"; done
Von Auersperg - 4
Von Neumann - 3
Kant - 2
Shakespeare - 1
$
The chosen answer seems to work if there are no spaces in the keys, but fails if there are:
$ declare -A authors
$ authors=(['Shakespeare']=1 ['Kant']=2 ['Von Neumann']=3 ['Von Auersperg']=4)
$ for k in "${!authors[@]}"; do echo $k ' - ' ${authors["$k"]}; done | sort -rn -k 3
Kant - 2
Shakespeare - 1
Von Neumann - 3
Von Auersperg - 4
$
