I have a select statement
sqlplus [credentials] select variable from table;
It returns 6 rows and I need to store them as an array in bash array variable.
array=(`sqlplus [credentials] select variable from table;`)
echo ${array[*]}
If your variables contain spaces and you want the array to have an element for each line of output (as opposed to each word of output), you also need to set your IFS. And you may want to use quotes when using the array:
SaveIFS="$IFS"
IFS=$'\n'
array=( $(sqlplus [credentials] select variable from table;) )
echo "${array[*]}"
IFS="$SaveIFS"
Related
I am new to Bash coding. I would like to concatenate a string to each element of a comma-separated strings "array".
This is an example of what I have in mind:
s=a,b,c
# Here a function to concatenate the string "_string" to each of them.
# Expected result:
a_string,b_string,c_string
One way:
$ s=a,b,c
$ echo ${s//,/_string,}_string
a_string,b_string,c_string
Using a proper array is generally a much more robust solution. It allows the values to contain literal commas, whitespace, etc.
s=(a b c)
printf '%s\n' "${s[#]/%/_string}"
As suggested by chepner, you can use IFS="," to merge the result with commas.
(IFS=","; echo "${s[#]/%/_string}")
(The subshell is useful to keep the scope of the IFS reassignment from leaking to the current shell.)
Simply, you could use a for loop
main() {
local input='a,b,c'
local append='_string'
# create an 'output' variable that is empty
local output=
# convert the input into an array called 'items' (without the commas)
IFS=',' read -ra items <<< "$input"
# loop over each item in the array, and append whatever string we want, in this case, '_string'
for item in "${items[#]}"; do
output+="${item}${append},"
done
# in the loop, the comma was re-added back. now, we must remove the so there are only commas _in between_ elements
output=${output%,}
echo "$output"
}
main
I've split it up in three steps:
Make it into an actual array.
Append _string to each element in the array using Parameter expansion.
Turn it back into a scalar (for which I've made a function called turn_array_into_scalar).
#!/bin/bash
function turn_array_into_scalar() {
local -n arr=$1 # -n makes `arr` a reference the array `s`
local IFS=$2 # set the field separator to ,
arr="${arr[*]}" # "join" over IFS and assign it back to `arr`
}
s=a,b,c
# make it into an array by turning , into newline and reading into `s`
readarray -t s < <(tr , '\n' <<< "$s")
# append _string to each string in the array by using parameter expansion
s=( "${s[#]/%/_string}" )
# use the function to make it into a scalar again and join over ,
turn_array_into_scalar s ,
echo "$s"
I have a variable ($OUTPUT) that contains the following name / value pairs:
member_id=4611686018429783292
platform=Xbox
platform_id=1
character_id=2305843009264966985
period_dt=2020-11-25 20:31:14.923158 UTC
mode=all Crucible modes
mode_id=5
activities_entered=18
activities_won=10
activities_lost=8
assists=103
kills=233
average_kill_distance=15.729613
total_kill_distance=3665
seconds_played=8535
deaths=118
average_lifespan=71.72269
total_lifespan=8463.277
opponents_defeated=336
efficiency=2.8474576
kills_deaths_ratio=1.9745762
kills_deaths_assists=2.411017
suicides=1
precision_kills=76
best_single_game_kills=-1
Each line ends with \n.
I want to loop through them, and parse them into an associative array, and the access the values in the array by the variable names:
while read line
do
key=${line%%=*}
value=${line#*=}
echo $key=$value
data[$key]="$value"
done < <(echo "$OUTPUT")
#this always prints the last value
echo ${data['seconds_played']}
This seems to work, i.e. key/value print the right values, but when I try to pull any values from the array, it always returns the last value (in this case -1).
I feel like im missing something obvious, but have been banging my head against it for a couple of hours.
UPDATE: My particular issue is I'm running a version of bash (3.2.57 on OSX) that doesn't support associative arrays). I'll mark the correct answer below.
Without declare -A data, then data is a normal array. In normal arrays expressions in [here] first undergo expansions, then arithmetic expansion. Inside arithmetic expansion unset variables are expanded to 0. You are effectively only just setting data[0]=something, because data[$key] is data[seconds_played] -> variable seconds_played is not defined, so it expands to data[0]
Add declare -A data and it "should work". You could also just:
declare -A data
while IFS== read -r key value; do
data["$key"]="$value"
done <<<"$OUTPUT"
Try declaring data as an associative array before populating it, eg:
$ typeset -A data # declare as an associative array
$ while read line
do
key=${line%%=*}
value=${line#*=}
echo $key=$value
data[$key]="$value"
done <<< "${OUTPUT}"
$ typeset -p data
declare -A data=([mode]="all Crucible modes" [period_dt]="2020-11-25 20:31:14.923158 UTC" [deaths]="118" [best_single_game_kills]="-1" [efficiency]="2.8474576" [precision_kills]="76" [activities_entered]="18" [seconds_played]="8535" [total_lifespan]="8463.277" [average_lifespan]="71.72269" [character_id]="2305843009264966985" [kills]="233" [activities_won]="10" [average_kill_distance]="15.729613" [activities_lost]="8" [mode_id]="5" [assists]="103" [suicides]="1" [total_kill_distance]="3665" [platform]="Xbox" [kills_deaths_ratio]="1.9745762" [platform_id]="1" [kills_deaths_assists]="2.411017" [opponents_defeated]="336" [member_id]="4611686018429783292" )
$ echo "${data['seconds_played']}"
8535
I'm trying to get back an array from perl to bash.
My perl scrip has an array and then I use return(#arr)
from my bash script I use
VAR = `perl....
when I echo VAR
I get the aray as 1 long string with all the array vars connected with no spaces.
Thanks
In the shell (and in Perl), backticks (``) capture the output of a command. However, Perl's return is normally for returning variables from subroutines - it does not produce output, so you probably want print instead. Also, in bash, array variables are declared with parentheses. So this works for me:
$ ARRAY=(`perl -wMstrict -le 'my #array = qw/foo bar baz/; print "#array"'`); \
echo "<${ARRAY[*]}> 0=${ARRAY[0]} 1=${ARRAY[1]} 2=${ARRAY[2]}"
<foo bar baz> 0=foo 1=bar 2=baz
In Perl, interpolating an array into a string (like "#array") will join the array with the special variable $" in between elements; that variable defaults to a single space. If you simply print #array, then the array elements will be joined by the variable $,, which is undef by default, meaning no space between the elements. This probably explains the behavior you mentioned ("the array vars connected with no spaces").
Note that the above will not work the way you expect if the elements of the array contain whitespace, because bash will split them into separate array elements. If your array does contain whitespace, then please provide an MCVE with sample data so we can perhaps make an alternative suggestion of how to return that back to bash. For example:
( # subshell so IFS is only affected locally
IFS=$'\n'
ARRAY=(`perl -wMstrict -e 'my #array = ("foo","bar","quz baz"); print join "\n", #array'`)
echo "0=<${ARRAY[0]}> 1=<${ARRAY[1]}> 2=<${ARRAY[2]}>"
)
Outputs: 0=<foo> 1=<bar> 2=<quz baz>
Here is one way using Bash word splitting, it will split the string on white space into the new array array:
array_str=$(perl -E '#a = 1..5; say "#a"')
array=( $array_str )
for item in ${array[#]} ; do
echo ": $item"
done
Output:
: 1
: 2
: 3
: 4
: 5
I'm wondering if anyone can help. I've not managed to find much in the way of examples and I'm not sure where to start coding wise either.
I have a file with the following contents...
VarA=/path/to/a
VarB=/path/to/b
VarC=/path/to/c
VarD=description of program
...
The columns are delimited by the '=' and some of the items in the 2nd column may contain gaps as they aren't just paths.
Ideally I'd love to open this in my script once and store the first column as the variable and the second as the value, for example...
echo $VarA
...
/path/to/a
echo $VarB
...
/path/to/a
Is this possible or am I living in a fairy land?
Thanks
You might be able to use the following loop:
while IFS== read -r name value; do
declare "$name=$value"
done < file.txt
Note, though, that a line like foo="3 5" would include the quotes in the value of the variable foo.
A minus sign or a special character isn't allowed in a variable name in Unix.
You may consider using BASH associative array for storing key and value together:
# declare an associative array
declare -A arr
# read file and populate the associative array
while IFS== read -r k v; do
arr["$k"]="$v"
done < file
# check output of our array
declare -p arr
declare -A arr='([VarA]="/path/to/a" [VarC]="/path/to/c" [VarB]="/path/to/b" [VarD]="description of program" )'
What about source my-file? It won't work with spaces though, but will work for what you've shared. This is an example:
reut#reut-home:~$ cat src
test=123
test2=abc/def
reut#reut-home:~$ echo $test $test2
reut#reut-home:~$ source src
reut#reut-home:~$ echo $test $test2
123 abc/def
I'm trying to understand a shell script written by a previous group member. there is this for loop. I can understand it's looping through a list ${!mylist[#]} but I've only seen ${mylist[#]} before, not ${!mylist[#]}.
What does the exclamation mark do here?
for i in ${!mylist[#]};
do
echo ${mylist[i]}
....
done
${!mylist[#]} returns the keys (or indices) to an an array. This differs from ${mylist[#]} which returns the values in the array.
As an example, let's consider this array:
$ arr=(abc def ghi)
In order to get its keys (or indices in this case):
$ echo "${!arr[#]}"
0 1 2
In order to get its values:
$ echo "${arr[#]}"
abc def ghi
From man bash:
It is possible to obtain the keys (indices) of an array as well
as the values. ${!name[#]} and ${!name[*]} expand to the indices
assigned in array variable name. The treatment when in double quotes
is similar to the expansion of the special parameters # and * within
double quotes.
Example using associative arrays
To show that the same applies to associative arrays:
$ declare -A Arr=([a]=one [b]=two)
$ echo "${!Arr[#]}"
a b
$ echo "${Arr[#]}"
one two