Related
I have an array in Bash, for example:
array=(a c b f 3 5)
I need to sort the array. Not just displaying the content in a sorted way, but to get a new array with the sorted elements. The new sorted array can be a completely new one or the old one.
You don't really need all that much code:
IFS=$'\n' sorted=($(sort <<<"${array[*]}"))
unset IFS
Supports whitespace in elements (as long as it's not a newline), and works in Bash 3.x.
e.g.:
$ array=("a c" b f "3 5")
$ IFS=$'\n' sorted=($(sort <<<"${array[*]}")); unset IFS
$ printf "[%s]\n" "${sorted[#]}"
[3 5]
[a c]
[b]
[f]
Note: #sorontar has pointed out that care is required if elements contain wildcards such as * or ?:
The sorted=($(...)) part is using the "split and glob" operator. You should turn glob off: set -f or set -o noglob or shopt -op noglob or an element of the array like * will be expanded to a list of files.
What's happening:
The result is a culmination six things that happen in this order:
IFS=$'\n'
"${array[*]}"
<<<
sort
sorted=($(...))
unset IFS
First, the IFS=$'\n'
This is an important part of our operation that affects the outcome of 2 and 5 in the following way:
Given:
"${array[*]}" expands to every element delimited by the first character of IFS
sorted=() creates elements by splitting on every character of IFS
IFS=$'\n' sets things up so that elements are expanded using a new line as the delimiter, and then later created in a way that each line becomes an element. (i.e. Splitting on a new line.)
Delimiting by a new line is important because that's how sort operates (sorting per line). Splitting by only a new line is not-as-important, but is needed preserve elements that contain spaces or tabs.
The default value of IFS is a space, a tab, followed by a new line, and would be unfit for our operation.
Next, the sort <<<"${array[*]}" part
<<<, called here strings, takes the expansion of "${array[*]}", as explained above, and feeds it into the standard input of sort.
With our example, sort is fed this following string:
a c
b
f
3 5
Since sort sorts, it produces:
3 5
a c
b
f
Next, the sorted=($(...)) part
The $(...) part, called command substitution, causes its content (sort <<<"${array[*]}) to run as a normal command, while taking the resulting standard output as the literal that goes where ever $(...) was.
In our example, this produces something similar to simply writing:
sorted=(3 5
a c
b
f
)
sorted then becomes an array that's created by splitting this literal on every new line.
Finally, the unset IFS
This resets the value of IFS to the default value, and is just good practice.
It's to ensure we don't cause trouble with anything that relies on IFS later in our script. (Otherwise we'd need to remember that we've switched things around--something that might be impractical for complex scripts.)
Original response:
array=(a c b "f f" 3 5)
readarray -t sorted < <(for a in "${array[#]}"; do echo "$a"; done | sort)
output:
$ for a in "${sorted[#]}"; do echo "$a"; done
3
5
a
b
c
f f
Note this version copes with values that contains special characters or whitespace (except newlines)
Note readarray is supported in bash 4+.
Edit Based on the suggestion by #Dimitre I had updated it to:
readarray -t sorted < <(printf '%s\0' "${array[#]}" | sort -z | xargs -0n1)
which has the benefit of even understanding sorting elements with newline characters embedded correctly. Unfortunately, as correctly signaled by #ruakh this didn't mean the the result of readarray would be correct, because readarray has no option to use NUL instead of regular newlines as line-separators.
If you don't need to handle special shell characters in the array elements:
array=(a c b f 3 5)
sorted=($(printf '%s\n' "${array[#]}"|sort))
With bash you'll need an external sorting program anyway.
With zsh no external programs are needed and special shell characters are easily handled:
% array=('a a' c b f 3 5); printf '%s\n' "${(o)array[#]}"
3
5
a a
b
c
f
ksh has set -s to sort ASCIIbetically.
Here's a pure Bash quicksort implementation:
#!/bin/bash
# quicksorts positional arguments
# return is in array qsort_ret
qsort() {
local pivot i smaller=() larger=()
qsort_ret=()
(($#==0)) && return 0
pivot=$1
shift
for i; do
# This sorts strings lexicographically.
if [[ $i < $pivot ]]; then
smaller+=( "$i" )
else
larger+=( "$i" )
fi
done
qsort "${smaller[#]}"
smaller=( "${qsort_ret[#]}" )
qsort "${larger[#]}"
larger=( "${qsort_ret[#]}" )
qsort_ret=( "${smaller[#]}" "$pivot" "${larger[#]}" )
}
Use as, e.g.,
$ array=(a c b f 3 5)
$ qsort "${array[#]}"
$ declare -p qsort_ret
declare -a qsort_ret='([0]="3" [1]="5" [2]="a" [3]="b" [4]="c" [5]="f")'
This implementation is recursive… so here's an iterative quicksort:
#!/bin/bash
# quicksorts positional arguments
# return is in array qsort_ret
# Note: iterative, NOT recursive! :)
qsort() {
(($#==0)) && return 0
local stack=( 0 $(($#-1)) ) beg end i pivot smaller larger
qsort_ret=("$#")
while ((${#stack[#]})); do
beg=${stack[0]}
end=${stack[1]}
stack=( "${stack[#]:2}" )
smaller=() larger=()
pivot=${qsort_ret[beg]}
for ((i=beg+1;i<=end;++i)); do
if [[ "${qsort_ret[i]}" < "$pivot" ]]; then
smaller+=( "${qsort_ret[i]}" )
else
larger+=( "${qsort_ret[i]}" )
fi
done
qsort_ret=( "${qsort_ret[#]:0:beg}" "${smaller[#]}" "$pivot" "${larger[#]}" "${qsort_ret[#]:end+1}" )
if ((${#smaller[#]}>=2)); then stack+=( "$beg" "$((beg+${#smaller[#]}-1))" ); fi
if ((${#larger[#]}>=2)); then stack+=( "$((end-${#larger[#]}+1))" "$end" ); fi
done
}
In both cases, you can change the order you use: I used string comparisons, but you can use arithmetic comparisons, compare wrt file modification time, etc. just use the appropriate test; you can even make it more generic and have it use a first argument that is the test function use, e.g.,
#!/bin/bash
# quicksorts positional arguments
# return is in array qsort_ret
# Note: iterative, NOT recursive! :)
# First argument is a function name that takes two arguments and compares them
qsort() {
(($#<=1)) && return 0
local compare_fun=$1
shift
local stack=( 0 $(($#-1)) ) beg end i pivot smaller larger
qsort_ret=("$#")
while ((${#stack[#]})); do
beg=${stack[0]}
end=${stack[1]}
stack=( "${stack[#]:2}" )
smaller=() larger=()
pivot=${qsort_ret[beg]}
for ((i=beg+1;i<=end;++i)); do
if "$compare_fun" "${qsort_ret[i]}" "$pivot"; then
smaller+=( "${qsort_ret[i]}" )
else
larger+=( "${qsort_ret[i]}" )
fi
done
qsort_ret=( "${qsort_ret[#]:0:beg}" "${smaller[#]}" "$pivot" "${larger[#]}" "${qsort_ret[#]:end+1}" )
if ((${#smaller[#]}>=2)); then stack+=( "$beg" "$((beg+${#smaller[#]}-1))" ); fi
if ((${#larger[#]}>=2)); then stack+=( "$((end-${#larger[#]}+1))" "$end" ); fi
done
}
Then you can have this comparison function:
compare_mtime() { [[ $1 -nt $2 ]]; }
and use:
$ qsort compare_mtime *
$ declare -p qsort_ret
to have the files in current folder sorted by modification time (newest first).
NOTE. These functions are pure Bash! no external utilities, and no subshells! they are safe wrt any funny symbols you may have (spaces, newline characters, glob characters, etc.).
NOTE2. The test [[ $i < $pivot ]] is correct. It uses the lexicographical string comparison. If your array only contains integers and you want to sort numerically, use ((i < pivot)) instead.
Please don't edit this answer to change that. It has already been edited (and rolled back) a couple of times. The test I gave here is correct and corresponds to the output given in the example: the example uses both strings and numbers, and the purpose is to sort it in lexicographical order. Using ((i < pivot)) in this case is wrong.
tl;dr:
Sort array a_in and store the result in a_out (elements must not have embedded newlines[1]
):
Bash v4+:
readarray -t a_out < <(printf '%s\n' "${a_in[#]}" | sort)
Bash v3:
IFS=$'\n' read -d '' -r -a a_out < <(printf '%s\n' "${a_in[#]}" | sort)
Advantages over antak's solution:
You needn't worry about accidental globbing (accidental interpretation of the array elements as filename patterns), so no extra command is needed to disable globbing (set -f, and set +f to restore it later).
You needn't worry about resetting IFS with unset IFS.[2]
Optional reading: explanation and sample code
The above combines Bash code with external utility sort for a solution that works with arbitrary single-line elements and either lexical or numerical sorting (optionally by field):
Performance: For around 20 elements or more, this will be faster than a pure Bash solution - significantly and increasingly so once you get beyond around 100 elements.
(The exact thresholds will depend on your specific input, machine, and platform.)
The reason it is fast is that it avoids Bash loops.
printf '%s\n' "${a_in[#]}" | sort performs the sorting (lexically, by default - see sort's POSIX spec):
"${a_in[#]}" safely expands to the elements of array a_in as individual arguments, whatever they contain (including whitespace).
printf '%s\n' then prints each argument - i.e., each array element - on its own line, as-is.
Note the use of a process substitution (<(...)) to provide the sorted output as input to read / readarray (via redirection to stdin, <), because read / readarray must run in the current shell (must not run in a subshell) in order for output variable a_out to be visible to the current shell (for the variable to remain defined in the remainder of the script).
Reading sort's output into an array variable:
Bash v4+: readarray -t a_out reads the individual lines output by sort into the elements of array variable a_out, without including the trailing \n in each element (-t).
Bash v3: readarray doesn't exist, so read must be used:
IFS=$'\n' read -d '' -r -a a_out tells read to read into array (-a) variable a_out, reading the entire input, across lines (-d ''), but splitting it into array elements by newlines (IFS=$'\n'. $'\n', which produces a literal newline (LF), is a so-called ANSI C-quoted string).
(-r, an option that should virtually always be used with read, disables unexpected handling of \ characters.)
Annotated sample code:
#!/usr/bin/env bash
# Define input array `a_in`:
# Note the element with embedded whitespace ('a c')and the element that looks like
# a glob ('*'), chosen to demonstrate that elements with line-internal whitespace
# and glob-like contents are correctly preserved.
a_in=( 'a c' b f 5 '*' 10 )
# Sort and store output in array `a_out`
# Saving back into `a_in` is also an option.
IFS=$'\n' read -d '' -r -a a_out < <(printf '%s\n' "${a_in[#]}" | sort)
# Bash 4.x: use the simpler `readarray -t`:
# readarray -t a_out < <(printf '%s\n' "${a_in[#]}" | sort)
# Print sorted output array, line by line:
printf '%s\n' "${a_out[#]}"
Due to use of sort without options, this yields lexical sorting (digits sort before letters, and digit sequences are treated lexically, not as numbers):
*
10
5
a c
b
f
If you wanted numerical sorting by the 1st field, you'd use sort -k1,1n instead of just sort, which yields (non-numbers sort before numbers, and numbers sort correctly):
*
a c
b
f
5
10
[1] To handle elements with embedded newlines, use the following variant (Bash v4+, with GNU sort):
readarray -d '' -t a_out < <(printf '%s\0' "${a_in[#]}" | sort -z).
Michał Górny's helpful answer has a Bash v3 solution.
[2] While IFS is set in the Bash v3 variant, the change is scoped to the command.
By contrast, what follows IFS=$'\n' in antak's answer is an assignment rather than a command, in which case the IFS change is global.
In the 3-hour train trip from Munich to Frankfurt (which I had trouble to reach because Oktoberfest starts tomorrow) I was thinking about my first post. Employing a global array is a much better idea for a general sort function. The following function handles arbitary strings (newlines, blanks etc.):
declare BSORT=()
function bubble_sort()
{ #
# #param [ARGUMENTS]...
#
# Sort all positional arguments and store them in global array BSORT.
# Without arguments sort this array. Return the number of iterations made.
#
# Bubble sorting lets the heaviest element sink to the bottom.
#
(($# > 0)) && BSORT=("$#")
local j=0 ubound=$((${#BSORT[*]} - 1))
while ((ubound > 0))
do
local i=0
while ((i < ubound))
do
if [ "${BSORT[$i]}" \> "${BSORT[$((i + 1))]}" ]
then
local t="${BSORT[$i]}"
BSORT[$i]="${BSORT[$((i + 1))]}"
BSORT[$((i + 1))]="$t"
fi
((++i))
done
((++j))
((--ubound))
done
echo $j
}
bubble_sort a c b 'z y' 3 5
echo ${BSORT[#]}
This prints:
3 5 a b c z y
The same output is created from
BSORT=(a c b 'z y' 3 5)
bubble_sort
echo ${BSORT[#]}
Note that probably Bash internally uses smart-pointers, so the swap-operation could be cheap (although I doubt it). However, bubble_sort demonstrates that more advanced functions like merge_sort are also in the reach of the shell language.
Another solution that uses external sort and copes with any special characters (except for NULs :)). Should work with bash-3.2 and GNU or BSD sort (sadly, POSIX doesn't include -z).
local e new_array=()
while IFS= read -r -d '' e; do
new_array+=( "${e}" )
done < <(printf "%s\0" "${array[#]}" | LC_ALL=C sort -z)
First look at the input redirection at the end. We're using printf built-in to write out the array elements, zero-terminated. The quoting makes sure array elements are passed as-is, and specifics of shell printf cause it to reuse the last part of format string for each remaining parameter. That is, it's equivalent to something like:
for e in "${array[#]}"; do
printf "%s\0" "${e}"
done
The null-terminated element list is then passed to sort. The -z option causes it to read null-terminated elements, sort them and output null-terminated as well. If you needed to get only the unique elements, you can pass -u since it is more portable than uniq -z. The LC_ALL=C ensures stable sort order independently of locale — sometimes useful for scripts. If you want the sort to respect locale, remove that.
The <() construct obtains the descriptor to read from the spawned pipeline, and < redirects the standard input of the while loop to it. If you need to access the standard input inside the pipe, you may use another descriptor — exercise for the reader :).
Now, back to the beginning. The read built-in reads output from the redirected stdin. Setting empty IFS disables word splitting which is unnecessary here — as a result, read reads the whole 'line' of input to the single provided variable. -r option disables escape processing that is undesired here as well. Finally, -d '' sets the line delimiter to NUL — that is, tells read to read zero-terminated strings.
As a result, the loop is executed once for every successive zero-terminated array element, with the value being stored in e. The example just puts the items in another array but you may prefer to process them directly :).
Of course, that's just one of the many ways of achieving the same goal. As I see it, it is simpler than implementing complete sorting algorithm in bash and in some cases it will be faster. It handles all special characters including newlines and should work on most of the common systems. Most importantly, it may teach you something new and awesome about bash :).
Keep it simple ;)
In the following example, the array b is the sorted version of the array a!
The second line echos each item of the array a, then pipes them to the sort command, and the output is used to initiate the array b.
a=(2 3 1)
b=( $( for x in ${a[#]}; do echo $x; done | sort ) )
echo ${b[#]} # output: 1 2 3
min sort:
#!/bin/bash
array=(.....)
index_of_element1=0
while (( ${index_of_element1} < ${#array[#]} )); do
element_1="${array[${index_of_element1}]}"
index_of_element2=$((index_of_element1 + 1))
index_of_min=${index_of_element1}
min_element="${element_1}"
for element_2 in "${array[#]:$((index_of_element1 + 1))}"; do
min_element="`printf "%s\n%s" "${min_element}" "${element_2}" | sort | head -n+1`"
if [[ "${min_element}" == "${element_2}" ]]; then
index_of_min=${index_of_element2}
fi
let index_of_element2++
done
array[${index_of_element1}]="${min_element}"
array[${index_of_min}]="${element_1}"
let index_of_element1++
done
try this:
echo ${array[#]} | awk 'BEGIN{RS=" ";} {print $1}' | sort
Output will be:
3
5
a
b
c
f
Problem solved.
If you can compute a unique integer for each element in the array, like this:
tab='0123456789abcdefghijklmnopqrstuvwxyz'
# build the reversed ordinal map
for ((i = 0; i < ${#tab}; i++)); do
declare -g ord_${tab:i:1}=$i
done
function sexy_int() {
local sum=0
local i ch ref
for ((i = 0; i < ${#1}; i++)); do
ch="${1:i:1}"
ref="ord_$ch"
(( sum += ${!ref} ))
done
return $sum
}
sexy_int hello
echo "hello -> $?"
sexy_int world
echo "world -> $?"
then, you can use these integers as array indexes, because Bash always use sparse array, so no need to worry about unused indexes:
array=(a c b f 3 5)
for el in "${array[#]}"; do
sexy_int "$el"
sorted[$?]="$el"
done
echo "${sorted[#]}"
Pros. Fast.
Cons. Duplicated elements are merged, and it can be impossible to map contents to 32-bit unique integers.
array=(a c b f 3 5)
new_array=($(echo "${array[#]}" | sed 's/ /\n/g' | sort))
echo ${new_array[#]}
echo contents of new_array will be:
3 5 a b c f
There is a workaround for the usual problem of spaces and newlines:
Use a character that is not in the original array (like $'\1' or $'\4' or similar).
This function gets the job done:
# Sort an Array may have spaces or newlines with a workaround (wa=$'\4')
sortarray(){ local wa=$'\4' IFS=''
if [[ $* =~ [$wa] ]]; then
echo "$0: error: array contains the workaround char" >&2
exit 1
fi
set -f; local IFS=$'\n' x nl=$'\n'
set -- $(printf '%s\n' "${#//$nl/$wa}" | sort -n)
for x
do sorted+=("${x//$wa/$nl}")
done
}
This will sort the array:
$ array=( a b 'c d' $'e\nf' $'g\1h')
$ sortarray "${array[#]}"
$ printf '<%s>\n' "${sorted[#]}"
<a>
<b>
<c d>
<e
f>
<gh>
This will complain that the source array contains the workaround character:
$ array=( a b 'c d' $'e\nf' $'g\4h')
$ sortarray "${array[#]}"
./script: error: array contains the workaround char
description
We set two local variables wa (workaround char) and a null IFS
Then (with ifs null) we test that the whole array $*.
Does not contain any woraround char [[ $* =~ [$wa] ]].
If it does, raise a message and signal an error: exit 1
Avoid filename expansions: set -f
Set a new value of IFS (IFS=$'\n') a loop variable x and a newline var (nl=$'\n').
We print all values of the arguments received (the input array $#).
but we replace any new line by the workaround char "${#//$nl/$wa}".
send those values to be sorted sort -n.
and place back all the sorted values in the positional arguments set --.
Then we assign each argument one by one (to preserve newlines).
in a loop for x
to a new array: sorted+=(…)
inside quotes to preserve any existing newline.
restoring the workaround to a newline "${x//$wa/$nl}".
done
This question looks closely related. And BTW, here's a mergesort in Bash (without external processes):
mergesort() {
local -n -r input_reference="$1"
local -n output_reference="$2"
local -r -i size="${#input_reference[#]}"
local merge previous
local -a -i runs indices
local -i index previous_idx merged_idx \
run_a_idx run_a_stop \
run_b_idx run_b_stop
output_reference=("${input_reference[#]}")
if ((size == 0)); then return; fi
previous="${output_reference[0]}"
runs=(0)
for ((index = 0;;)) do
for ((++index;; ++index)); do
if ((index >= size)); then break 2; fi
if [[ "${output_reference[index]}" < "$previous" ]]; then break; fi
previous="${output_reference[index]}"
done
previous="${output_reference[index]}"
runs+=(index)
done
runs+=(size)
while (("${#runs[#]}" > 2)); do
indices=("${!runs[#]}")
merge=("${output_reference[#]}")
for ((index = 0; index < "${#indices[#]}" - 2; index += 2)); do
merged_idx=runs[indices[index]]
run_a_idx=merged_idx
previous_idx=indices[$((index + 1))]
run_a_stop=runs[previous_idx]
run_b_idx=runs[previous_idx]
run_b_stop=runs[indices[$((index + 2))]]
unset runs[previous_idx]
while ((run_a_idx < run_a_stop && run_b_idx < run_b_stop)); do
if [[ "${merge[run_a_idx]}" < "${merge[run_b_idx]}" ]]; then
output_reference[merged_idx++]="${merge[run_a_idx++]}"
else
output_reference[merged_idx++]="${merge[run_b_idx++]}"
fi
done
while ((run_a_idx < run_a_stop)); do
output_reference[merged_idx++]="${merge[run_a_idx++]}"
done
while ((run_b_idx < run_b_stop)); do
output_reference[merged_idx++]="${merge[run_b_idx++]}"
done
done
done
}
declare -ar input=({z..a}{z..a})
declare -a output
mergesort input output
echo "${input[#]}"
echo "${output[#]}"
Many thanks to the people that answered before me. Using their excellent input, bash documentation and ideas from other treads, this is what works perfectly for me without IFS change
array=("a \n c" b f "3 5")
Using process substitution and read array in bash > v4.4 WITH EOL character
readarray -t sorted < <(sort < <(printf '%s\n' "${array[#]}"))
Using process substitution and read array in bash > v4.4 WITH NULL character
readarray -td '' sorted < <(sort -z < <(printf '%s\0' "${array[#]}"))
Finally we verify with
printf "[%s]\n" "${sorted[#]}"
output is
[3 5]
[a \n c]
[b]
[f]
Please, let me know if that is a correct test for embedded /n as both solutions produce the same result, but the first one is not supposed to work properly with embedded /n
I am not convinced that you'll need an external sorting program in Bash.
Here is my implementation for the simple bubble-sort algorithm.
function bubble_sort()
{ #
# Sorts all positional arguments and echoes them back.
#
# Bubble sorting lets the heaviest (longest) element sink to the bottom.
#
local array=($#) max=$(($# - 1))
while ((max > 0))
do
local i=0
while ((i < max))
do
if [ ${array[$i]} \> ${array[$((i + 1))]} ]
then
local t=${array[$i]}
array[$i]=${array[$((i + 1))]}
array[$((i + 1))]=$t
fi
((i += 1))
done
((max -= 1))
done
echo ${array[#]}
}
array=(a c b f 3 5)
echo " input: ${array[#]}"
echo "output: $(bubble_sort ${array[#]})"
This shall print:
input: a c b f 3 5
output: 3 5 a b c f
a=(e b 'c d')
shuf -e "${a[#]}" | sort >/tmp/f
mapfile -t g </tmp/f
Great answers here. Learned a lot. After reading them all, I figure I'd throw my hat into the ring. I think this is the shortest method (and probably faster as it doesn't do much shell script parsing, though there is the matter of the spawning of printf and sort, but they're only called once each) and handles whitespace in the data:
a=(3 "2 a" 1) # Setup!
IFS=$'\n' b=( $(printf "%s\n" "${a[#]}" | sort) ); unset IFS # Sort!
printf "'%s' " "${b[#]}"; # Success!
Outputs:
'1' '2 a' '3'
Note that the IFS change is limited in scope to the line it is on. if you know that the array has no whitespace in it, you don't need the IFS modification.
Inspiration was from #yas's answer and #Alcamtar comments.
EDIT
Oh, I somehow missed the actually accepted answer which is even shorter than mine. Doh!
IFS=$'\n' sorted=($(sort <<<"${array[*]}")); unset IFS
Turns out that the unset is required because this is a variable assignment that has no command.
I'd recommend going to that answer because it has some interesting stuff on globbing which could be relevant if the array has wildcards in it. It also has a detailed description as to what is happening.
EDIT 2
GNU has an extension in which sort delimits records using \0 which is good if you have LFs in your data. However, when it gets returned to the shell to be assign to an array, I don't see a good way convert it so that the shell will delimit on \0, because even setting IFS=$'\0', the shell doesn't like it and doesn't properly break it up.
array=(z 'b c'); { set "${array[#]}"; printf '%s\n' "$#"; } \
| sort \
| mapfile -t array; declare -p array
declare -a array=([0]="b c" [1]="z")
Open an inline function {...} to get a fresh set of positional arguments (e.g. $1, $2, etc).
Copy the array to the positional arguments. (e.g. set "${array[#]}" will copy the nth array argument to the nth positional argument. Note the quotes preserve whitespace that may be contained in an array element).
Print each positional argument (e.g. printf '%s\n' "$#" will print each positional argument on its own line. Again, note the quotes preserve whitespace that may be contained in each positional argument).
Then sort does its thing.
Read the stream into an array with mapfile (e.g. mapfile -t array reads each line into the variable array and the -t ignores the \n in each line).
Dump the array to show its been sorted.
As a function:
set +m
shopt -s lastpipe
sort_array() {
declare -n ref=$1
set "${ref[#]}"
printf '%s\n' "$#"
| sort \
| mapfile -t $ref
}
then
array=(z y x); sort_array array; declare -p array
declare -a array=([0]="x" [1]="y" [2]="z")
I look forward to being ripped apart by all the UNIX gurus! :)
sorted=($(echo ${array[#]} | tr " " "\n" | sort))
In the spirit of bash / linux, I would pipe the best command-line tool for each step. sort does the main job but needs input separated by newline instead of space, so the very simple pipeline above simply does:
Echo array content --> replace space by newline --> sort
$() is to echo the result
($()) is to put the "echoed result" in an array
Note: as #sorontar mentioned in a comment to a different question:
The sorted=($(...)) part is using the "split and glob" operator. You should turn glob off: set -f or set -o noglob or shopt -op noglob or an element of the array like * will be expanded to a list of files.
I need to order these 2 arrays, I don't care about the format of the output, I only need it to be ordered in order to compare them but this doesn't seem to work, although it works with simpler text. I also tried removing the --field-separator='"'
DIG_1=("sampletext""zzz""ms=ms91608007""asdas")
DIG_2=("zzz""ms=ms91608007""sampletext""asdas")
echo "unsorted:"
echo ${DIG_1[*]}
echo ${DIG_2[*]}
IFS=$'\n' sorted=($(sort --field-separator='"' <<<"${DIG_1[*]}")); unset IFS
IFS=$'\n' sorted2=($(sort --field-separator='"' <<<"${DIG_2[*]}")); unset IFS
echo "sorted:"
echo ${sorted[*]}
echo ${sorted2[*]}
And the output I get is:
unsorted:
sampletextzzzms=ms91608007asdas
zzzms=ms91608007sampletextasdas
sorted:
sampletextzzzms=ms91608007asdas
zzzms=ms91608007sampletextasdas
How Can I fix this? I want it to be, for example:
unsorted:
sampletextzzzms=ms91608007asdas
zzzms=ms91608007sampletextasdas
sorted:
asdasms=ms91608007sampletextzzz
asdasms=ms91608007sampletextzzz
There's no reason to use an array to store one element.
Since you need to keep the double quotes, you need to make efforts to preserve them:
DIG_1='"sampletext""zzz""ms=ms91608007""asdas"'
Otherwise the double quotes will be removed by the shell: 3.5.9 Quote Removal
When you use VAR=value some_command, that variable is only
set for the duration of some_command -- bash puts that variable in the environment for the command, not into the shell's own catalog of variables. Subsequently unsetting the
variable is not required -- unsetting the IFS variable is potentially harmful
for the rest of the program
sort won't sort the fields within a record, it's for sorting records against each other.
To accomplish what you want, this will do:
sorted_1=$(grep -Po '(?<=").*?(?=")' <<<"$DIG_1" | sort | paste -s -d "")
As anubhava mentioned in the comments, the current code is creating arrays of single values, ie:
$ DIG_1=("sampletext""zzz""ms=ms91608007""asdas")
$ typeset -p DIG_1
declare -a DIG_1=([0]="sampletextzzzms=ms91608007asdas")
$ DIG_2=("zzz""ms=ms91608007""sampletext""asdas")
$ typeset -p DIG_2
declare -a DIG_2=([0]="zzzms=ms91608007sampletextasdas")
Assuming the OP really does want an array, and that the array elements will be utilized in later code, we need a way to delimit the items of the array, and the easiest way to do this is with some white space, eg:
$ DIG_1=("sample text" "zzz" "ms=ms91608007" "asdas")
$ typeset -p DIG_1
declare -a DIG_1=([0]="sample text" [1]="zzz" [2]="ms=ms91608007" [3]="asdas")
$ DIG_2=("zzz" "ms=ms91608007" "sample text" "asdas")
$ typeset -p DIG_2
declare -a DIG_2=([0]="zzz" [1]="ms=ms91608007" [2]="sample text" [3]="asdas")
NOTE: I've added a single space to change "sampletext" to "sample text" so that we can see how a space is treated a) as part of the data vs b) as a delimiter.
NOTE: Assuming OPs code is generating the questionable array assignments (eg, DIG_1=("sampletext""zzz""ms=ms91608007""asdas")), it may make more sense to look into ways to 'fix' the array generator than to complicate the code by trying to figure out how to treat these single strings as a 4-part array definition.
Also, since the sample output (current vs desired) shows no double quotes I'm guessing this means the double quotes are not part of the actual data but rather just delimiters.
Now that we have an actual array of elements we can look at sorting the arrays and storing the results into additional (sorted) arrays, eg:
$ IFS=$'\n' sorted=($(printf "%s\n" "${DIG_1[#]}" | sort))
$ typeset -p sorted
declare -a sorted=([0]="asdas" [1]="ms=ms91608007" [2]="sample text" [3]="zzz")
$ IFS=$'\n' sorted2=($(printf "%s\n" "${DIG_2[#]}" | sort))
$ typeset -p sorted2
declare -a sorted2=([0]="asdas" [1]="ms=ms91608007" [2]="sample text" [3]="zzz")
At this point we now have 2 sets of arrays ... 1) original data (DIG_1[#] and DIG_2[#]) and 2) sorted (sorted[#] and sorted2[#]).
The OP can then slice-n-dice the data as desired, as well as print the contents of the arrays in any desired format, eg:
# print array elements on a single line with no delimiters, storing the results
# in variables for later use/comparison/display
$ printf -v srt "%s" "${sorted[#]}"
$ typeset -p srt
declare -- srt="asdasms=ms91608007sample textzzz"
$ echo "${srt}"
asdasms=ms91608007sample textzzz
$ printf -v srt2 "%s" "${sorted2[#]}"
$ typeset -p srt2
declare -- srt2="asdasms=ms91608007sample textzzz"
$ echo "${srt2}"
asdasms=ms91608007sample textzzz
How can I get just the filenames into an array using the cat command?
How I've been trying:
array=()
while IFS= read -r -d $'\0'; do
array+=("$REPLY")
done < <(cat /proc/swaps | grep "swap")
This either grabs all the information from the output into an array, or just doesn't work. How can I successfully get my expected output of [/swapfile, /dev/hda1, /some/other/swap] into an array form using the cat command?
readarray array < <(awk '/swap/{print $1}' /proc/swaps)
Bash introduced readarray in version 4 which can take the place of the while read loop. readarray is the solution you want.
here is the syntax
readarray variable < inputfile
echo "${variable[0]}" ' to print the first element in array
We know that the sed command loops over each line of a file and for each line, it loops over the given commands list and does something. But when the file is extremely large, the time and resource cost on the repeating operation may be terrible.
Suppose that I have an array of line numbers which I want to use as addresses to delete or print with sed command (e.g. A=(20000 30000 50000 90000)) and there is a VERY LARGE object file.
The easiest way may be:
(Remark by #John1024, careful about the line number changes for each loop)
( for NL in ${A[#]}; do sed "$NL d" $very_large_file; done; )>.temp_file;
cp .temp_file $very_large_file; rm .temp_file
The problem of the code above is that, for each indexed line number of the array, it needs to loop over the whole file.
To avoid this, one can:
#COMM=`echo "${A[#]}" | sed 's/\s/d;/g;s/$/d'`;
#sed -i "$COMM" $very_large_file;
#Edited: Better with direct parameter expansion:
sed -i "${A[#]/%/d;}" $very_large_file;
It first print the array and replace its SPACE and the END_OF_LINE with the d command of sed, so that the string looks like "20000d;30000d;50000d;90000d"; on the second line, we treat this string as the command list of sed. The result is that with this code, it only loops over the file for once.
More over, for in-place operation (argument -i), one cannot quit using q with sed even though the greatest line number of interest has passed, because if so, the lines after the that line (e.g. 90001+) will disappear (It seems that the in-place operation is just overwriting the file with stdout).
Better ideas?
(Reply to #user unknown:) I think it could be even more efficient if we manage to "quit" the loop once all indexed lines have passed. We can't, using sed -i, for the aforementioned reasons. Printing each line to a file cost more time than copying a file (e.g. cat file1 > file2 and cp file1 file2). We may benefit from this concept, using any other methods or tools. This is what I expect.
PS: The points of this question are "Lines location" and "Efficiency"; the "delete lines" operation is just an example. For real tasks, there are much more - append/insert/substituting, field separating, cases judgement followed by read from/write to files, calculations etc.
In order words, it may invoke all kind of operations, creating sub-shells or not, caring about the variable passing, ... so, the tools to use should allow me to line processing, and the problem is how to get myself onto the lines of interest, doing all kinds operations.
Any comments are appreciated.
First make a copy to a testfile for checking the results.
You want to sort the linenumbers, highest first.
echo "${a[#]}" | sed 's/\s/\n/g' | sort -rn
You can feed commands into ed using printf:
printf "%s\n" "command1" "command2" w q testfile | ed -s testfile
Combine these
printf "%s\n" $(echo "${a[#]}" | sed 's/\s/\n/g' | sort -rn | sed 's/$/d/') w q |
ed -s testfile
Edit (tx #Ed_Morton):
This can be written in less steps with
printf "%s\n" $(printf '%sd\n' "${a[#]}" | sort -rn ) w q | ed -s testfile
I can not remove the sort, because each delete instruction is counting the linenumbers from 1.
I tried to find a command for editing the file without redirecting to another, but I started with the remark that you should make a copy. I have no choice, I have to upvote the straight forward awk solution that doesn't need a sort.
sed is for doing s/old/new, that is all, and when you add a shell loop to the mix you've really gone off the rails (see https://unix.stackexchange.com/q/169716/133219). To delete lines whose numbers are stored in an array is (using seq to generate input since no sample input/output provided in the question):
$ a=( 3 7 8 )
$ seq 10 |
awk -v a="${a[*]}" 'BEGIN{split(a,tmp); for (i in tmp) nrs[tmp[i]]} !(NR in nrs)'
1
2
4
5
6
9
10
and if you wanted to stop processing with awk once the last target line has been deleted and let tail finish the job then you could figure out the max value in the array up front and then do awk on just the part up to that last target line:
max=$( printf '%s\n' "${a[#]}" | sort -rn | head -1 )
head -"$max" file | awk '...' file > out
tail +"$((max+1))" file >> out
idk if that'd really be any faster than just letting awk process the whole file since awk is very efficient, especially when you're not referencing any fields and so it doesn't do any field splitting, but you could give it a try.
You could generate an intermediate sed command file from your lines.
echo ${A[#]} | sort -n > lines_to_delete
min=`head -1` lines_to_delete
max=`head -1` lines_to_delete
# skip to first and from last line, delete the others
sed -i -e 1d -e ${linecount}d -e 's#$#d#' lines_to_delete
head -${min} input > output
sed -f lines_to_delete input >> output
tail -${max} input >> output
mv output input
The below script:
#!/bin/bash
otscurrent="
AAA,33854,4528,38382,12
BBB,83917,12296,96213,13
CCC,20399,5396,25795,21
DDD,27198,4884,32082,15
EEE,2472,981,3453,28
FFF,3207,851,4058,21
GGG,30621,4595,35216,13
HHH,8450,1504,9954,15
III,4963,2157,7120,30
JJJ,51,59,110,54
KKK,87,123,210,59
LLL,573,144,717,20
MMM,617,1841,2458,75
NNN,234,76,310,25
OOO,12433,1908,14341,13
PPP,10627,1428,12055,12
QQQ,510,514,1024,50
RRR,1361,687,2048,34
SSS,1,24,25,96
TTT,0,5,5,100
UUU,294,1606,1900,85
"
IFS="," array1=(${otscurrent})
echo ${array1[4]}
Prints:
$ ./test.sh
12
BBB
I'm trying to get it to just print 12... And I am not even sure how to make it just print row 5 column 4
The variable is an output of a sqlquery that has been parsed with several sed commands to change the formatting to csv.
otscurrent="$(sqlplus64 user/password#dbserverip/db as sysdba #query.sql |
sed '1,11d; /^-/d; s/[[:space:]]\{1,\}/,/g; $d' |
sed '$d'|sed '$d'|sed '$d' | sed '$d' |
sed 's/Used,MB/Used MB/g' |
sed 's/Free,MB/Free MB/g' |
sed 's/Total,MB/Total MB/g' |
sed 's/Pct.,Free/Pct. Free/g' |
sed '1b;/^Name/d' |
sed '/^$/d'
)"
Ultimately I would like to be able to call on a row and column and run statements on the values.
Initially i was piping that into :
awk -F "," 'NR>1{ if($5 < 10) { printf "%-30s%-10s%-10s%-10s%-10s\n", $1,$2,$3,$4,$5"%"; } else { echo "Nothing to do" } }')"
Which works but I couldn't run commands from if else ... or atleaste I didn't know how.
If you have bash 4.0 or newer, an associative array is an appropriate way to store data in this kind of form.
otscurrent=${otscurrent#$'\n'} # strip leading newline present in your sample data
declare -A data=( )
row=0
while IFS=, read -r -a line; do
for idx in "${!line[#]}"; do
data["$row,$idx"]=${line[$idx]}
done
(( row += 1 ))
done <<<"$otscurrent"
This lets you access each individual item:
echo "${data[0,0]}" # first field of first line
echo "${data[9,0]}" # first field of tenth line
echo "${data[9,1]}" # second field of tenth line
"I'm trying to get it to just print 12..."
The issue is that IFS="," splits on commas and there is no comma between 12 and BBB. If you want those to be separate elements, add a newline to IFS. Thus, replace:
IFS="," array1=(${otscurrent})
With:
IFS=$',\n' array1=(${otscurrent})
Output:
$ bash test.sh
12
All you need to print the value of the 4th column on the 5th row is:
$ awk -F, 'NR==5{print $4}' <<< "$otscurrent"
3453
and just remember that in awk row (record) and column (field) numbers start at 1, not 0. Some more examples:
$ awk -F, 'NR==1{print $5}' <<< "$otscurrent"
12
$ awk -F, 'NR==2{print $1}' <<< "$otscurrent"
BBB
$ awk -F, '$5 > 50' <<< "$otscurrent"
JJJ,51,59,110,54
KKK,87,123,210,59
MMM,617,1841,2458,75
SSS,1,24,25,96
TTT,0,5,5,100
UUU,294,1606,1900,85
If you'd like to avoid all of the complexity and simply parse your SQL output to produce what you want without 20 sed commands in between, post a new question showing the raw sqlplus output as the input and what you want finally output and someone will post a brief, clear, simple, efficient awk script to do it all at one time, or maybe 2 commands if you still want an intermediate CSV for some reason.