Related
I want to write a script that loops through 15 strings (array possibly?) Is that possible?
Something like:
for databaseName in listOfNames
then
# Do something
end
You can use it like this:
## declare an array variable
declare -a arr=("element1" "element2" "element3")
## now loop through the above array
for i in "${arr[#]}"
do
echo "$i"
# or do whatever with individual element of the array
done
# You can access them using echo "${arr[0]}", "${arr[1]}" also
Also works for multi-line array declaration
declare -a arr=("element1"
"element2" "element3"
"element4"
)
That is possible, of course.
for databaseName in a b c d e f; do
# do something like: echo $databaseName
done
See Bash Loops for, while and until for details.
None of those answers include a counter...
#!/bin/bash
## declare an array variable
declare -a array=("one" "two" "three")
# get length of an array
arraylength=${#array[#]}
# use for loop to read all values and indexes
for (( i=0; i<${arraylength}; i++ ));
do
echo "index: $i, value: ${array[$i]}"
done
Output:
index: 0, value: one
index: 1, value: two
index: 2, value: three
Yes
for Item in Item1 Item2 Item3 Item4 ;
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
To preserve spaces; single or double quote list entries and double quote list expansions.
for Item in 'Item 1' 'Item 2' 'Item 3' 'Item 4' ;
do
echo "$Item"
done
Output:
Item 1
Item 2
Item 3
Item 4
To make list over multiple lines
for Item in Item1 \
Item2 \
Item3 \
Item4
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
Simple list variable
List=( Item1 Item2 Item3 )
or
List=(
Item1
Item2
Item3
)
Display the list variable:
echo ${List[*]}
Output:
Item1 Item2 Item3
Loop through the list:
for Item in ${List[*]}
do
echo $Item
done
Output:
Item1
Item2
Item3
Create a function to go through a list:
Loop(){
for item in ${*} ;
do
echo ${item}
done
}
Loop ${List[*]}
Using the declare keyword (command) to create the list, which is technically called an array:
declare -a List=(
"element 1"
"element 2"
"element 3"
)
for entry in "${List[#]}"
do
echo "$entry"
done
Output:
element 1
element 2
element 3
Creating an associative array. A dictionary:
declare -A continent
continent[Vietnam]=Asia
continent[France]=Europe
continent[Argentina]=America
for item in "${!continent[#]}";
do
printf "$item is in ${continent[$item]} \n"
done
Output:
Argentina is in America
Vietnam is in Asia
France is in Europe
CSV variables or files in to a list. Changing the internal field separator from a space, to what ever you want. In the example below it is changed to a comma
List="Item 1,Item 2,Item 3"
Backup_of_internal_field_separator=$IFS
IFS=,
for item in $List;
do
echo $item
done
IFS=$Backup_of_internal_field_separator
Output:
Item 1
Item 2
Item 3
If need to number them:
`
this is called a back tick. Put the command inside back ticks.
`command`
It is next to the number one on your keyboard and or above the tab key, on a standard American English language keyboard.
List=()
Start_count=0
Step_count=0.1
Stop_count=1
for Item in `seq $Start_count $Step_count $Stop_count`
do
List+=(Item_$Item)
done
for Item in ${List[*]}
do
echo $Item
done
Output is:
Item_0.0
Item_0.1
Item_0.2
Item_0.3
Item_0.4
Item_0.5
Item_0.6
Item_0.7
Item_0.8
Item_0.9
Item_1.0
Becoming more familiar with bashes behavior:
Create a list in a file
cat <<EOF> List_entries.txt
Item1
Item 2
'Item 3'
"Item 4"
Item 7 : *
"Item 6 : * "
"Item 6 : *"
Item 8 : $PWD
'Item 8 : $PWD'
"Item 9 : $PWD"
EOF
Read the list file in to a list and display
List=$(cat List_entries.txt)
echo $List
echo '$List'
echo "$List"
echo ${List[*]}
echo '${List[*]}'
echo "${List[*]}"
echo ${List[#]}
echo '${List[#]}'
echo "${List[#]}"
BASH commandline reference manual: Special meaning of certain characters or words to the shell.
In the same spirit as 4ndrew's answer:
listOfNames="RA
RB
R C
RD"
# To allow for other whitespace in the string:
# 1. add double quotes around the list variable, or
# 2. see the IFS note (under 'Side Notes')
for databaseName in "$listOfNames" # <-- Note: Added "" quotes.
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R C
# RD
B. No whitespace in the names:
listOfNames="RA
RB
R C
RD"
for databaseName in $listOfNames # Note: No quotes
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R
# C
# RD
Notes
In the second example, using listOfNames="RA RB R C RD" has the same output.
Other ways to bring in data include:
stdin (listed below),
variables,
an array (the accepted answer),
a file...
Read from stdin
# line delimited (each databaseName is stored on a line)
while read databaseName
do
echo "$databaseName" # i.e. do action / processing of $databaseName here...
done # <<< or_another_input_method_here
the bash IFS "field separator to line" [1] delimiter can be specified in the script to allow other whitespace (i.e. IFS='\n', or for MacOS IFS='\r')
I like the accepted answer also :) -- I've include these snippets as other helpful ways that also answer the question.
Including #!/bin/bash at the top of the script file indicates the execution environment.
It took me months to figure out how to code this simply :)
Other Sources
(while read loop)
You can use the syntax of ${arrayName[#]}
#!/bin/bash
# declare an array called files, that contains 3 values
files=( "/etc/passwd" "/etc/group" "/etc/hosts" )
for i in "${files[#]}"
do
echo "$i"
done
Surprised that nobody's posted this yet -- if you need the indices of the elements while you're looping through the array, you can do this:
arr=(foo bar baz)
for i in ${!arr[#]}
do
echo $i "${arr[i]}"
done
Output:
0 foo
1 bar
2 baz
I find this a lot more elegant than the "traditional" for-loop style (for (( i=0; i<${#arr[#]}; i++ ))).
(${!arr[#]} and $i don't need to be quoted because they're just numbers; some would suggest quoting them anyway, but that's just personal preference.)
This is also easy to read:
FilePath=(
"/tmp/path1/" #FilePath[0]
"/tmp/path2/" #FilePath[1]
)
#Loop
for Path in "${FilePath[#]}"
do
echo "$Path"
done
I used this approach for my GitHub updates, and I found it simple.
## declare an array variable
arr_variable=("kofi" "kwame" "Ama")
## now loop through the above array
for i in "${arr_variable[#]}"
do
echo "$i"
done
You can iterate through bash array values using a counter with three-expression (C style) to read all values and indexes for loops syntax:
declare -a kofi=("kofi" "kwame" "Ama")
# get the length of the array
length=${#kofi[#]}
for (( j=0; j<${length}; j++ ));
do
print (f "Current index %d with value %s\n" $j "${kofi[$j]}")
done
Simple way :
arr=("sharlock" "bomkesh" "feluda" ) ##declare array
len=${#arr[*]} # it returns the array length
#iterate with while loop
i=0
while [ $i -lt $len ]
do
echo ${arr[$i]}
i=$((i+1))
done
#iterate with for loop
for i in $arr
do
echo $i
done
#iterate with splice
echo ${arr[#]:0:3}
listOfNames="db_one db_two db_three"
for databaseName in $listOfNames
do
echo $databaseName
done
or just
for databaseName in db_one db_two db_three
do
echo $databaseName
done
Implicit array for script or functions:
In addition to anubhava's correct answer: If basic syntax for loop is:
for var in "${arr[#]}" ;do ...$var... ;done
there is a special case in bash:
When running a script or a function, arguments passed at command lines will be assigned to $# array variable, you can access by $1, $2, $3, and so on.
This can be populated (for test) by
set -- arg1 arg2 arg3 ...
A loop over this array could be written simply:
for item ;do
echo "This is item: $item."
done
Note that the reserved work in is not present and no array name too!
Sample:
set -- arg1 arg2 arg3 ...
for item ;do
echo "This is item: $item."
done
This is item: arg1.
This is item: arg2.
This is item: arg3.
This is item: ....
Note that this is same than
for item in "$#";do
echo "This is item: $item."
done
Then into a script:
#!/bin/bash
for item ;do
printf "Doing something with '%s'.\n" "$item"
done
Save this in a script myscript.sh, chmod +x myscript.sh, then
./myscript.sh arg1 arg2 arg3 ...
Doing something with 'arg1'.
Doing something with 'arg2'.
Doing something with 'arg3'.
Doing something with '...'.
Same in a function:
myfunc() { for item;do cat <<<"Working about '$item'."; done ; }
Then
myfunc item1 tiem2 time3
Working about 'item1'.
Working about 'tiem2'.
Working about 'time3'.
The declare array doesn't work for Korn shell. Use the below example for the Korn shell:
promote_sla_chk_lst="cdi xlob"
set -A promote_arry $promote_sla_chk_lst
for i in ${promote_arry[*]};
do
echo $i
done
Try this. It is working and tested.
for k in "${array[#]}"
do
echo $k
done
# For accessing with the echo command: echo ${array[0]}, ${array[1]}
This is similar to user2533809's answer, but each file will be executed as a separate command.
#!/bin/bash
names="RA
RB
R C
RD"
while read -r line; do
echo line: "$line"
done <<< "$names"
If you are using Korn shell, there is "set -A databaseName ", else there is "declare -a databaseName"
To write a script working on all shells,
set -A databaseName=("db1" "db2" ....) ||
declare -a databaseName=("db1" "db2" ....)
# now loop
for dbname in "${arr[#]}"
do
echo "$dbname" # or whatever
done
It should be work on all shells.
What I really needed for this was something like this:
for i in $(the_array); do something; done
For instance:
for i in $(ps -aux | grep vlc | awk '{ print $2 }'); do kill -9 $i; done
(Would kill all processes with vlc in their name)
How you loop through an array, depends on the presence of new line characters. With new line characters separating the array elements, the array can be referred to as "$array", otherwise it should be referred to as "${array[#]}". The following script will make it clear:
#!/bin/bash
mkdir temp
mkdir temp/aaa
mkdir temp/bbb
mkdir temp/ccc
array=$(ls temp)
array1=(aaa bbb ccc)
array2=$(echo -e "aaa\nbbb\nccc")
echo '$array'
echo "$array"
echo
for dirname in "$array"; do
echo "$dirname"
done
echo
for dirname in "${array[#]}"; do
echo "$dirname"
done
echo
echo '$array1'
echo "$array1"
echo
for dirname in "$array1"; do
echo "$dirname"
done
echo
for dirname in "${array1[#]}"; do
echo "$dirname"
done
echo
echo '$array2'
echo "$array2"
echo
for dirname in "$array2"; do
echo "$dirname"
done
echo
for dirname in "${array2[#]}"; do
echo "$dirname"
done
rmdir temp/aaa
rmdir temp/bbb
rmdir temp/ccc
rmdir temp
Possible first line of every Bash script/session:
say() { for line in "${#}" ; do printf "%s\n" "${line}" ; done ; }
Use e.g.:
$ aa=( 7 -4 -e ) ; say "${aa[#]}"
7
-4
-e
May consider: echo interprets -e as option here
Single line looping,
declare -a listOfNames=('db_a' 'db_b' 'db_c')
for databaseName in ${listOfNames[#]}; do echo $databaseName; done;
you will get an output like this,
db_a
db_b
db_c
I loop through an array of my projects for a git pull update:
#!/bin/sh
projects="
web
ios
android
"
for project in $projects do
cd $HOME/develop/$project && git pull
end
I have a file like this below:
-bash-4.2$ cat a1.txt
0 10.95.187.87 5444 up 0.333333 primary 0 false 0
1 10.95.187.88 5444 up 0.333333 standby 1 true 0
2 10.95.187.89 5444 up 0.333333 standby 0 false 0
I want to fetch the data from the above file into a 2D array.
Can you please help me with a suitable way to put into an array.
Also post putting we need put a condition to check whether the value in the 4th column is UP or DOWN. If it's UP then OK, if its down then below command needs to be executed.
-bash-4.2$ pcp_attach_node -w -U pcpuser -h localhost -p 9898 0
(The value at the end is getting fetched from the 1st column.
You could try something like that:
while read -r line; do
declare -a array=( $line ) # use IFS
echo "${array[0]}"
echo "${array[1]}" # and so on
if [[ "$array[3]" ]]; then
echo execute command...
fi
done < a1.txt
Or:
while read -r -a array; do
if [[ "$array[3]" ]]; then
echo execute command...
fi
done < a1.txt
This works only if field are space separated (any kind of space).
You could probably mix that with regexp if you need more precise control of the format.
Firstly, I don't think you can have 2D arrays in bash. But you can however store lines into a 1-D array.
Here is a script ,parse1a.sh, to demonstrate emulation of 2D arrays for the type of data you included:
#!/bin/bash
function get_element () {
line=${ARRAY[$1]}
echo $line | awk "{print \$$(($2+1))}" #+1 since awk is one-based
}
function set_element () {
line=${ARRAY[$1]}
declare -a SUBARRAY=($line)
SUBARRAY[$(($2))]=$3
ARRAY[$1]="${SUBARRAY[#]}"
}
ARRAY=()
while IFS='' read -r line || [[ -n "$line" ]]; do
#echo $line
ARRAY+=("$line")
done < "$1"
echo "Full array contents printout:"
printf "%s\n" "${ARRAY[#]}" # Full array contents printout.
for line in "${ARRAY[#]}"; do
#echo $line
if [ "$(echo $line | awk '{print $4}')" == "down" ]; then
echo "Replace this with what to do for down"
else
echo "...and any action for up - if required"
fi
done
echo "Element access of [2,3]:"
echo "get_element 2 3 : "
get_element 2 3
echo "set_element 2 3 left: "
set_element 2 3 left
echo "get_element 2 3 : "
get_element 2 3
echo "Full array contents printout:"
printf "%s\n" "${ARRAY[#]}" # Full array contents printout.
It can be executed by:
./parsea1 a1.txt
Hope this is close to what you are looking for. Note that this code will loose all indenting spaces during manipulation, but a formatted update of the lines could solve that.
I want to write a script that loops through 15 strings (array possibly?) Is that possible?
Something like:
for databaseName in listOfNames
then
# Do something
end
You can use it like this:
## declare an array variable
declare -a arr=("element1" "element2" "element3")
## now loop through the above array
for i in "${arr[#]}"
do
echo "$i"
# or do whatever with individual element of the array
done
# You can access them using echo "${arr[0]}", "${arr[1]}" also
Also works for multi-line array declaration
declare -a arr=("element1"
"element2" "element3"
"element4"
)
That is possible, of course.
for databaseName in a b c d e f; do
# do something like: echo $databaseName
done
See Bash Loops for, while and until for details.
None of those answers include a counter...
#!/bin/bash
## declare an array variable
declare -a array=("one" "two" "three")
# get length of an array
arraylength=${#array[#]}
# use for loop to read all values and indexes
for (( i=0; i<${arraylength}; i++ ));
do
echo "index: $i, value: ${array[$i]}"
done
Output:
index: 0, value: one
index: 1, value: two
index: 2, value: three
Yes
for Item in Item1 Item2 Item3 Item4 ;
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
To preserve spaces; single or double quote list entries and double quote list expansions.
for Item in 'Item 1' 'Item 2' 'Item 3' 'Item 4' ;
do
echo "$Item"
done
Output:
Item 1
Item 2
Item 3
Item 4
To make list over multiple lines
for Item in Item1 \
Item2 \
Item3 \
Item4
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
Simple list variable
List=( Item1 Item2 Item3 )
or
List=(
Item1
Item2
Item3
)
Display the list variable:
echo ${List[*]}
Output:
Item1 Item2 Item3
Loop through the list:
for Item in ${List[*]}
do
echo $Item
done
Output:
Item1
Item2
Item3
Create a function to go through a list:
Loop(){
for item in ${*} ;
do
echo ${item}
done
}
Loop ${List[*]}
Using the declare keyword (command) to create the list, which is technically called an array:
declare -a List=(
"element 1"
"element 2"
"element 3"
)
for entry in "${List[#]}"
do
echo "$entry"
done
Output:
element 1
element 2
element 3
Creating an associative array. A dictionary:
declare -A continent
continent[Vietnam]=Asia
continent[France]=Europe
continent[Argentina]=America
for item in "${!continent[#]}";
do
printf "$item is in ${continent[$item]} \n"
done
Output:
Argentina is in America
Vietnam is in Asia
France is in Europe
CSV variables or files in to a list. Changing the internal field separator from a space, to what ever you want. In the example below it is changed to a comma
List="Item 1,Item 2,Item 3"
Backup_of_internal_field_separator=$IFS
IFS=,
for item in $List;
do
echo $item
done
IFS=$Backup_of_internal_field_separator
Output:
Item 1
Item 2
Item 3
If need to number them:
`
this is called a back tick. Put the command inside back ticks.
`command`
It is next to the number one on your keyboard and or above the tab key, on a standard American English language keyboard.
List=()
Start_count=0
Step_count=0.1
Stop_count=1
for Item in `seq $Start_count $Step_count $Stop_count`
do
List+=(Item_$Item)
done
for Item in ${List[*]}
do
echo $Item
done
Output is:
Item_0.0
Item_0.1
Item_0.2
Item_0.3
Item_0.4
Item_0.5
Item_0.6
Item_0.7
Item_0.8
Item_0.9
Item_1.0
Becoming more familiar with bashes behavior:
Create a list in a file
cat <<EOF> List_entries.txt
Item1
Item 2
'Item 3'
"Item 4"
Item 7 : *
"Item 6 : * "
"Item 6 : *"
Item 8 : $PWD
'Item 8 : $PWD'
"Item 9 : $PWD"
EOF
Read the list file in to a list and display
List=$(cat List_entries.txt)
echo $List
echo '$List'
echo "$List"
echo ${List[*]}
echo '${List[*]}'
echo "${List[*]}"
echo ${List[#]}
echo '${List[#]}'
echo "${List[#]}"
BASH commandline reference manual: Special meaning of certain characters or words to the shell.
In the same spirit as 4ndrew's answer:
listOfNames="RA
RB
R C
RD"
# To allow for other whitespace in the string:
# 1. add double quotes around the list variable, or
# 2. see the IFS note (under 'Side Notes')
for databaseName in "$listOfNames" # <-- Note: Added "" quotes.
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R C
# RD
B. No whitespace in the names:
listOfNames="RA
RB
R C
RD"
for databaseName in $listOfNames # Note: No quotes
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R
# C
# RD
Notes
In the second example, using listOfNames="RA RB R C RD" has the same output.
Other ways to bring in data include:
stdin (listed below),
variables,
an array (the accepted answer),
a file...
Read from stdin
# line delimited (each databaseName is stored on a line)
while read databaseName
do
echo "$databaseName" # i.e. do action / processing of $databaseName here...
done # <<< or_another_input_method_here
the bash IFS "field separator to line" [1] delimiter can be specified in the script to allow other whitespace (i.e. IFS='\n', or for MacOS IFS='\r')
I like the accepted answer also :) -- I've include these snippets as other helpful ways that also answer the question.
Including #!/bin/bash at the top of the script file indicates the execution environment.
It took me months to figure out how to code this simply :)
Other Sources
(while read loop)
You can use the syntax of ${arrayName[#]}
#!/bin/bash
# declare an array called files, that contains 3 values
files=( "/etc/passwd" "/etc/group" "/etc/hosts" )
for i in "${files[#]}"
do
echo "$i"
done
Surprised that nobody's posted this yet -- if you need the indices of the elements while you're looping through the array, you can do this:
arr=(foo bar baz)
for i in ${!arr[#]}
do
echo $i "${arr[i]}"
done
Output:
0 foo
1 bar
2 baz
I find this a lot more elegant than the "traditional" for-loop style (for (( i=0; i<${#arr[#]}; i++ ))).
(${!arr[#]} and $i don't need to be quoted because they're just numbers; some would suggest quoting them anyway, but that's just personal preference.)
This is also easy to read:
FilePath=(
"/tmp/path1/" #FilePath[0]
"/tmp/path2/" #FilePath[1]
)
#Loop
for Path in "${FilePath[#]}"
do
echo "$Path"
done
I used this approach for my GitHub updates, and I found it simple.
## declare an array variable
arr_variable=("kofi" "kwame" "Ama")
## now loop through the above array
for i in "${arr_variable[#]}"
do
echo "$i"
done
You can iterate through bash array values using a counter with three-expression (C style) to read all values and indexes for loops syntax:
declare -a kofi=("kofi" "kwame" "Ama")
# get the length of the array
length=${#kofi[#]}
for (( j=0; j<${length}; j++ ));
do
print (f "Current index %d with value %s\n" $j "${kofi[$j]}")
done
Simple way :
arr=("sharlock" "bomkesh" "feluda" ) ##declare array
len=${#arr[*]} # it returns the array length
#iterate with while loop
i=0
while [ $i -lt $len ]
do
echo ${arr[$i]}
i=$((i+1))
done
#iterate with for loop
for i in $arr
do
echo $i
done
#iterate with splice
echo ${arr[#]:0:3}
listOfNames="db_one db_two db_three"
for databaseName in $listOfNames
do
echo $databaseName
done
or just
for databaseName in db_one db_two db_three
do
echo $databaseName
done
Implicit array for script or functions:
In addition to anubhava's correct answer: If basic syntax for loop is:
for var in "${arr[#]}" ;do ...$var... ;done
there is a special case in bash:
When running a script or a function, arguments passed at command lines will be assigned to $# array variable, you can access by $1, $2, $3, and so on.
This can be populated (for test) by
set -- arg1 arg2 arg3 ...
A loop over this array could be written simply:
for item ;do
echo "This is item: $item."
done
Note that the reserved work in is not present and no array name too!
Sample:
set -- arg1 arg2 arg3 ...
for item ;do
echo "This is item: $item."
done
This is item: arg1.
This is item: arg2.
This is item: arg3.
This is item: ....
Note that this is same than
for item in "$#";do
echo "This is item: $item."
done
Then into a script:
#!/bin/bash
for item ;do
printf "Doing something with '%s'.\n" "$item"
done
Save this in a script myscript.sh, chmod +x myscript.sh, then
./myscript.sh arg1 arg2 arg3 ...
Doing something with 'arg1'.
Doing something with 'arg2'.
Doing something with 'arg3'.
Doing something with '...'.
Same in a function:
myfunc() { for item;do cat <<<"Working about '$item'."; done ; }
Then
myfunc item1 tiem2 time3
Working about 'item1'.
Working about 'tiem2'.
Working about 'time3'.
The declare array doesn't work for Korn shell. Use the below example for the Korn shell:
promote_sla_chk_lst="cdi xlob"
set -A promote_arry $promote_sla_chk_lst
for i in ${promote_arry[*]};
do
echo $i
done
Try this. It is working and tested.
for k in "${array[#]}"
do
echo $k
done
# For accessing with the echo command: echo ${array[0]}, ${array[1]}
This is similar to user2533809's answer, but each file will be executed as a separate command.
#!/bin/bash
names="RA
RB
R C
RD"
while read -r line; do
echo line: "$line"
done <<< "$names"
If you are using Korn shell, there is "set -A databaseName ", else there is "declare -a databaseName"
To write a script working on all shells,
set -A databaseName=("db1" "db2" ....) ||
declare -a databaseName=("db1" "db2" ....)
# now loop
for dbname in "${arr[#]}"
do
echo "$dbname" # or whatever
done
It should be work on all shells.
What I really needed for this was something like this:
for i in $(the_array); do something; done
For instance:
for i in $(ps -aux | grep vlc | awk '{ print $2 }'); do kill -9 $i; done
(Would kill all processes with vlc in their name)
How you loop through an array, depends on the presence of new line characters. With new line characters separating the array elements, the array can be referred to as "$array", otherwise it should be referred to as "${array[#]}". The following script will make it clear:
#!/bin/bash
mkdir temp
mkdir temp/aaa
mkdir temp/bbb
mkdir temp/ccc
array=$(ls temp)
array1=(aaa bbb ccc)
array2=$(echo -e "aaa\nbbb\nccc")
echo '$array'
echo "$array"
echo
for dirname in "$array"; do
echo "$dirname"
done
echo
for dirname in "${array[#]}"; do
echo "$dirname"
done
echo
echo '$array1'
echo "$array1"
echo
for dirname in "$array1"; do
echo "$dirname"
done
echo
for dirname in "${array1[#]}"; do
echo "$dirname"
done
echo
echo '$array2'
echo "$array2"
echo
for dirname in "$array2"; do
echo "$dirname"
done
echo
for dirname in "${array2[#]}"; do
echo "$dirname"
done
rmdir temp/aaa
rmdir temp/bbb
rmdir temp/ccc
rmdir temp
Possible first line of every Bash script/session:
say() { for line in "${#}" ; do printf "%s\n" "${line}" ; done ; }
Use e.g.:
$ aa=( 7 -4 -e ) ; say "${aa[#]}"
7
-4
-e
May consider: echo interprets -e as option here
Single line looping,
declare -a listOfNames=('db_a' 'db_b' 'db_c')
for databaseName in ${listOfNames[#]}; do echo $databaseName; done;
you will get an output like this,
db_a
db_b
db_c
I loop through an array of my projects for a git pull update:
#!/bin/sh
projects="
web
ios
android
"
for project in $projects do
cd $HOME/develop/$project && git pull
end
I've looked, but have only seen answers to one array being passed in a script.
I want to pass multiple arrays to a bash script that assigns them as individual variables as follows:
./myScript.sh ${array1[#]} ${array2[#]} ${array3[#]}
such that: var1=array1 and var2=array2 and var3=array3
I've tried multiple options, but doing variableName=("$#") combines all arrays together into each variable. I hope to have in my bash script a variable that represents each array.
The shell passes a single argument vector (that is to say, a simple C array of strings) off to a program being run. This is an OS-level limitation: There exists no method to pass structured data between two programs (any two programs, written in any language!) in an argument list, except by encoding that structure in the contents of the members of this array of C strings.
Approach: Length Prefixes
If efficiency is a goal (both in terms of ease-of-parsing and amount of space used out of the ARG_MAX limit on command-line and environment storage), one approach to consider is prefixing each array with an argument describing its length.
By providing length arguments, however, you can indicate which sections of that argument list are supposed to be part of a given array:
./myScript \
"${#array1[#]}" "${array1[#]}" \
"${#array2[#]}" "${array2[#]}" \
"${#array3[#]}" "${array3[#]}"
...then, inside the script, you can use the length arguments to split content back into arrays:
#!/usr/bin/env bash
array1=( "${#:2:$1}" ); shift "$(( $1 + 1 ))"
array2=( "${#:2:$1}" ); shift "$(( $1 + 1 ))"
array3=( "${#:2:$1}" ); shift "$(( $1 + 1 ))"
declare -p array1 array2 array3
If run as ./myScript 3 a b c 2 X Y 1 z, this has the output:
declare -a array1='([0]="a" [1]="b" [2]="c")'
declare -a array2='([0]="X" [1]="Y")'
declare -a array3='([0]="z")'
Approach: Per-Argument Array Name Prefixes
Incidentally, a practice common in the Python world (particularly with users of the argparse library) is to allow an argument to be passed more than once to amend to a given array. In shell, this would look like:
./myScript \
"${array1[#]/#/--array1=}" \
"${array2[#]/#/--array2=}" \
"${array3[#]/#/--array3=}"
and then the code to parse it might look like:
#!/usr/bin/env bash
declare -a args array1 array2 array3
while (( $# )); do
case $1 in
--array1=*) array1+=( "${1#*=}" );;
--array2=*) array2+=( "${1#*=}" );;
--array3=*) array3+=( "${1#*=}" );;
*) args+=( "$1" );;
esac
shift
done
Thus, if your original value were array1=( one two three ) array2=( aye bee ) array3=( "hello world" ), the calling convention would be:
./myScript --array1=one --array1=two --array1=three \
--array2=aye --array2=bee \
--array3="hello world"
Approach: NUL-Delimited Streams
Another approach is to pass a filename for each array from which a NUL-delimited list of its contents can be read. One chief advantage of this approach is that the size of array contents does not count against ARG_MAX, the OS-enforced command-line length limit. Moreover, with an operating system where such is available, the below does not create real on-disk files but instead creates /dev/fd-style links to FIFOs written to by subshells writing the contents of each array.
./myScript \
<( (( ${#array1[#]} )) && printf '%s\0' "${array1[#]}") \
<( (( ${#array2[#]} )) && printf '%s\0' "${array2[#]}") \
<( (( ${#array3[#]} )) && printf '%s\0' "${array3[#]}")
...and, to read (with bash 4.4 or newer, providing mapfile -d):
#!/usr/bin/env bash
mapfile -d '' array1 <"$1"
mapfile -d '' array2 <"$2"
mapfile -d '' array3 <"$3"
...or, to support older bash releases:
#!/usr/bin/env bash
declare -a array1 array2 array3
while IFS= read -r -d '' entry; do array1+=( "$entry" ); done <"$1"
while IFS= read -r -d '' entry; do array2+=( "$entry" ); done <"$2"
while IFS= read -r -d '' entry; do array3+=( "$entry" ); done <"$3"
Charles Duffy's response works perfectly well, but I would go about it a different way that makes it simpler to initialize var1, var2 and var3 in your script:
./myScript.sh "${#array1[#]} ${#array2[#]} ${#array3[#]}" \
"${array1[#]}" "${array2[#]}" "${array3[#]}"
Then in myScript.sh
#!/bin/bash
declare -ai lens=($1);
declare -a var1=("${#:2:lens[0]}") var2=("${#:2+lens[0]:lens[1]}") var3=("${#:2+lens[0]+lens[1]:lens[2]}");
Edit: Since Charles has simplified his solution, it is probably a better and more clear solution than mine.
Here is a code sample, which shows how to pass 2 arrays to a function. There is nothing more than in previous answers except it provides a full code example.
This is coded in bash 4.4.12, i.e. after bash 4.3 which would require a different coding approach. One array contains the texts to be colorized, and the other array contains the colors to be used for each of the text elements :
function cecho_multitext () {
# usage : cecho_multitext message_array color_array
# what it does : Multiple Colored-echo.
local -n array_msgs=$1
local -n array_colors=$2
# printf '1: %q\n' "${array_msgs[#]}"
# printf '2: %q\n' "${array_colors[#]}"
local i=0
local coloredstring=""
local normalcoloredstring=""
# check array counts
# echo "msg size : "${#array_msgs[#]}
# echo "col size : "${#array_colors[#]}
[[ "${#array_msgs[#]}" -ne "${#array_colors[#]}" ]] && exit 2
# build the colored string
for msg in "${array_msgs[#]}"
do
color=${array_colors[$i]}
coloredstring="$coloredstring $color $msg "
normalcoloredstring="$normalcoloredstring $msg"
# echo -e "coloredstring ($i): $coloredstring"
i=$((i+1))
done
# DEBUG
# echo -e "colored string : $coloredstring"
# echo -e "normal color string : $normal $normalcoloredstring"
# use either echo or printf as follows :
# echo -e "$coloredstring"
printf '%b\n' "${coloredstring}"
return
}
Calling the function :
#!/bin/bash
green='\E[32m'
cyan='\E[36m'
white='\E[37m'
normal=$(tput sgr0)
declare -a text=("one" "two" "three" )
declare -a color=("$white" "$green" "$cyan")
cecho_multitext text color
Job done :-)
I do prefer using base64 to encode and decode arrays like:
encode_array(){
local array=($#)
echo -n "${array[#]}" | base64
}
decode_array(){
echo -n "$#" | base64 -d
}
some_func(){
local arr1=($(decode_array $1))
local arr2=($(decode_array $2))
local arr3=($(decode_array $3))
echo arr1 has ${#arr1[#]} items, the second item is ${arr1[2]}
echo arr2 has ${#arr2[#]} items, the third item is ${arr2[3]}
echo arr3 has ${#arr3[#]} items, the here the contents ${arr3[#]}
}
a1=(ab cd ef)
a2=(gh ij kl nm)
a3=(op ql)
some_func "$(encode_array "${a1[#]}")" "$(encode_array "${a2[#]}")" "$(encode_array "${a3[#]}")"
The output is
arr1 has 3 items, the second item is cd
arr2 has 4 items, the third item is kl
arr3 has 2 items, the here the contents op ql
Anyway, that will not work with values that have tabs or spaces. If required, we need a more elaborated solution. something like:
encode_array()
{
for item in "$#";
do
echo -n "$item" | base64
done | paste -s -d , -
}
decode_array()
{
local IFS=$'\2'
local -a arr=($(echo "$1" | tr , "\n" |
while read encoded_array_item;
do
echo "$encoded_array_item" | base64 -d;
echo "$IFS"
done))
echo "${arr[*]}";
}
test_arrays_step1()
{
local IFS=$'\2'
local -a arr1=($(decode_array $1))
local -a arr2=($(decode_array $2))
local -a arr3=($(decode_array $3))
unset IFS
echo arr1 has ${#arr1[#]} items, the second item is ${arr1[1]}
echo arr2 has ${#arr2[#]} items, the third item is ${arr2[2]}
echo arr3 has ${#arr3[#]} items, the here the contents ${arr3[#]}
}
test_arrays()
{
local a1_2="$(echo -en "c\td")";
local a1=("a b" "$a1_2" "e f");
local a2=(gh ij kl nm);
local a3=(op ql );
a1_size=${#a1[#])};
resp=$(test_arrays_step1 "$(encode_array "${a1[#]}")" "$(encode_array "${a2[#]}")" "$(encode_array "${a3[#]}")");
echo -e "$resp" | grep arr1 | grep "arr1 has $a1_size, the second item is $a1_2" || echo but it should have only $a1_size items, with the second item as $a1_2
echo "$resp"
}
Based on the answers to this question you could try the following.
Define the arrays as variable on the shell:
array1=(1 2 3)
array2=(3 4 5)
array3=(6 7 8)
Have a script like this:
arg1=("${!1}")
arg2=("${!2}")
arg3=("${!3}")
echo "arg1 array=${arg1[#]}"
echo "arg1 #elem=${#arg1[#]}"
echo "arg2 array=${arg2[#]}"
echo "arg2 #elem=${#arg2[#]}"
echo "arg3 array=${arg3[#]}"
echo "arg3 #elem=${#arg3[#]}"
And call it like this:
. ./test.sh "array1[#]" "array2[#]" "array3[#]"
Note that the script will need to be sourced (. or source) so that it is executed in the current shell environment and not a sub shell.
I want to write a script that loops through 15 strings (array possibly?) Is that possible?
Something like:
for databaseName in listOfNames
then
# Do something
end
You can use it like this:
## declare an array variable
declare -a arr=("element1" "element2" "element3")
## now loop through the above array
for i in "${arr[#]}"
do
echo "$i"
# or do whatever with individual element of the array
done
# You can access them using echo "${arr[0]}", "${arr[1]}" also
Also works for multi-line array declaration
declare -a arr=("element1"
"element2" "element3"
"element4"
)
That is possible, of course.
for databaseName in a b c d e f; do
# do something like: echo $databaseName
done
See Bash Loops for, while and until for details.
None of those answers include a counter...
#!/bin/bash
## declare an array variable
declare -a array=("one" "two" "three")
# get length of an array
arraylength=${#array[#]}
# use for loop to read all values and indexes
for (( i=0; i<${arraylength}; i++ ));
do
echo "index: $i, value: ${array[$i]}"
done
Output:
index: 0, value: one
index: 1, value: two
index: 2, value: three
Yes
for Item in Item1 Item2 Item3 Item4 ;
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
To preserve spaces; single or double quote list entries and double quote list expansions.
for Item in 'Item 1' 'Item 2' 'Item 3' 'Item 4' ;
do
echo "$Item"
done
Output:
Item 1
Item 2
Item 3
Item 4
To make list over multiple lines
for Item in Item1 \
Item2 \
Item3 \
Item4
do
echo $Item
done
Output:
Item1
Item2
Item3
Item4
Simple list variable
List=( Item1 Item2 Item3 )
or
List=(
Item1
Item2
Item3
)
Display the list variable:
echo ${List[*]}
Output:
Item1 Item2 Item3
Loop through the list:
for Item in ${List[*]}
do
echo $Item
done
Output:
Item1
Item2
Item3
Create a function to go through a list:
Loop(){
for item in ${*} ;
do
echo ${item}
done
}
Loop ${List[*]}
Using the declare keyword (command) to create the list, which is technically called an array:
declare -a List=(
"element 1"
"element 2"
"element 3"
)
for entry in "${List[#]}"
do
echo "$entry"
done
Output:
element 1
element 2
element 3
Creating an associative array. A dictionary:
declare -A continent
continent[Vietnam]=Asia
continent[France]=Europe
continent[Argentina]=America
for item in "${!continent[#]}";
do
printf "$item is in ${continent[$item]} \n"
done
Output:
Argentina is in America
Vietnam is in Asia
France is in Europe
CSV variables or files in to a list. Changing the internal field separator from a space, to what ever you want. In the example below it is changed to a comma
List="Item 1,Item 2,Item 3"
Backup_of_internal_field_separator=$IFS
IFS=,
for item in $List;
do
echo $item
done
IFS=$Backup_of_internal_field_separator
Output:
Item 1
Item 2
Item 3
If need to number them:
`
this is called a back tick. Put the command inside back ticks.
`command`
It is next to the number one on your keyboard and or above the tab key, on a standard American English language keyboard.
List=()
Start_count=0
Step_count=0.1
Stop_count=1
for Item in `seq $Start_count $Step_count $Stop_count`
do
List+=(Item_$Item)
done
for Item in ${List[*]}
do
echo $Item
done
Output is:
Item_0.0
Item_0.1
Item_0.2
Item_0.3
Item_0.4
Item_0.5
Item_0.6
Item_0.7
Item_0.8
Item_0.9
Item_1.0
Becoming more familiar with bashes behavior:
Create a list in a file
cat <<EOF> List_entries.txt
Item1
Item 2
'Item 3'
"Item 4"
Item 7 : *
"Item 6 : * "
"Item 6 : *"
Item 8 : $PWD
'Item 8 : $PWD'
"Item 9 : $PWD"
EOF
Read the list file in to a list and display
List=$(cat List_entries.txt)
echo $List
echo '$List'
echo "$List"
echo ${List[*]}
echo '${List[*]}'
echo "${List[*]}"
echo ${List[#]}
echo '${List[#]}'
echo "${List[#]}"
BASH commandline reference manual: Special meaning of certain characters or words to the shell.
In the same spirit as 4ndrew's answer:
listOfNames="RA
RB
R C
RD"
# To allow for other whitespace in the string:
# 1. add double quotes around the list variable, or
# 2. see the IFS note (under 'Side Notes')
for databaseName in "$listOfNames" # <-- Note: Added "" quotes.
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R C
# RD
B. No whitespace in the names:
listOfNames="RA
RB
R C
RD"
for databaseName in $listOfNames # Note: No quotes
do
echo "$databaseName" # (i.e. do action / processing of $databaseName here...)
done
# Outputs
# RA
# RB
# R
# C
# RD
Notes
In the second example, using listOfNames="RA RB R C RD" has the same output.
Other ways to bring in data include:
stdin (listed below),
variables,
an array (the accepted answer),
a file...
Read from stdin
# line delimited (each databaseName is stored on a line)
while read databaseName
do
echo "$databaseName" # i.e. do action / processing of $databaseName here...
done # <<< or_another_input_method_here
the bash IFS "field separator to line" [1] delimiter can be specified in the script to allow other whitespace (i.e. IFS='\n', or for MacOS IFS='\r')
I like the accepted answer also :) -- I've include these snippets as other helpful ways that also answer the question.
Including #!/bin/bash at the top of the script file indicates the execution environment.
It took me months to figure out how to code this simply :)
Other Sources
(while read loop)
You can use the syntax of ${arrayName[#]}
#!/bin/bash
# declare an array called files, that contains 3 values
files=( "/etc/passwd" "/etc/group" "/etc/hosts" )
for i in "${files[#]}"
do
echo "$i"
done
Surprised that nobody's posted this yet -- if you need the indices of the elements while you're looping through the array, you can do this:
arr=(foo bar baz)
for i in ${!arr[#]}
do
echo $i "${arr[i]}"
done
Output:
0 foo
1 bar
2 baz
I find this a lot more elegant than the "traditional" for-loop style (for (( i=0; i<${#arr[#]}; i++ ))).
(${!arr[#]} and $i don't need to be quoted because they're just numbers; some would suggest quoting them anyway, but that's just personal preference.)
This is also easy to read:
FilePath=(
"/tmp/path1/" #FilePath[0]
"/tmp/path2/" #FilePath[1]
)
#Loop
for Path in "${FilePath[#]}"
do
echo "$Path"
done
I used this approach for my GitHub updates, and I found it simple.
## declare an array variable
arr_variable=("kofi" "kwame" "Ama")
## now loop through the above array
for i in "${arr_variable[#]}"
do
echo "$i"
done
You can iterate through bash array values using a counter with three-expression (C style) to read all values and indexes for loops syntax:
declare -a kofi=("kofi" "kwame" "Ama")
# get the length of the array
length=${#kofi[#]}
for (( j=0; j<${length}; j++ ));
do
print (f "Current index %d with value %s\n" $j "${kofi[$j]}")
done
Simple way :
arr=("sharlock" "bomkesh" "feluda" ) ##declare array
len=${#arr[*]} # it returns the array length
#iterate with while loop
i=0
while [ $i -lt $len ]
do
echo ${arr[$i]}
i=$((i+1))
done
#iterate with for loop
for i in $arr
do
echo $i
done
#iterate with splice
echo ${arr[#]:0:3}
listOfNames="db_one db_two db_three"
for databaseName in $listOfNames
do
echo $databaseName
done
or just
for databaseName in db_one db_two db_three
do
echo $databaseName
done
Implicit array for script or functions:
In addition to anubhava's correct answer: If basic syntax for loop is:
for var in "${arr[#]}" ;do ...$var... ;done
there is a special case in bash:
When running a script or a function, arguments passed at command lines will be assigned to $# array variable, you can access by $1, $2, $3, and so on.
This can be populated (for test) by
set -- arg1 arg2 arg3 ...
A loop over this array could be written simply:
for item ;do
echo "This is item: $item."
done
Note that the reserved work in is not present and no array name too!
Sample:
set -- arg1 arg2 arg3 ...
for item ;do
echo "This is item: $item."
done
This is item: arg1.
This is item: arg2.
This is item: arg3.
This is item: ....
Note that this is same than
for item in "$#";do
echo "This is item: $item."
done
Then into a script:
#!/bin/bash
for item ;do
printf "Doing something with '%s'.\n" "$item"
done
Save this in a script myscript.sh, chmod +x myscript.sh, then
./myscript.sh arg1 arg2 arg3 ...
Doing something with 'arg1'.
Doing something with 'arg2'.
Doing something with 'arg3'.
Doing something with '...'.
Same in a function:
myfunc() { for item;do cat <<<"Working about '$item'."; done ; }
Then
myfunc item1 tiem2 time3
Working about 'item1'.
Working about 'tiem2'.
Working about 'time3'.
The declare array doesn't work for Korn shell. Use the below example for the Korn shell:
promote_sla_chk_lst="cdi xlob"
set -A promote_arry $promote_sla_chk_lst
for i in ${promote_arry[*]};
do
echo $i
done
Try this. It is working and tested.
for k in "${array[#]}"
do
echo $k
done
# For accessing with the echo command: echo ${array[0]}, ${array[1]}
This is similar to user2533809's answer, but each file will be executed as a separate command.
#!/bin/bash
names="RA
RB
R C
RD"
while read -r line; do
echo line: "$line"
done <<< "$names"
If you are using Korn shell, there is "set -A databaseName ", else there is "declare -a databaseName"
To write a script working on all shells,
set -A databaseName=("db1" "db2" ....) ||
declare -a databaseName=("db1" "db2" ....)
# now loop
for dbname in "${arr[#]}"
do
echo "$dbname" # or whatever
done
It should be work on all shells.
What I really needed for this was something like this:
for i in $(the_array); do something; done
For instance:
for i in $(ps -aux | grep vlc | awk '{ print $2 }'); do kill -9 $i; done
(Would kill all processes with vlc in their name)
How you loop through an array, depends on the presence of new line characters. With new line characters separating the array elements, the array can be referred to as "$array", otherwise it should be referred to as "${array[#]}". The following script will make it clear:
#!/bin/bash
mkdir temp
mkdir temp/aaa
mkdir temp/bbb
mkdir temp/ccc
array=$(ls temp)
array1=(aaa bbb ccc)
array2=$(echo -e "aaa\nbbb\nccc")
echo '$array'
echo "$array"
echo
for dirname in "$array"; do
echo "$dirname"
done
echo
for dirname in "${array[#]}"; do
echo "$dirname"
done
echo
echo '$array1'
echo "$array1"
echo
for dirname in "$array1"; do
echo "$dirname"
done
echo
for dirname in "${array1[#]}"; do
echo "$dirname"
done
echo
echo '$array2'
echo "$array2"
echo
for dirname in "$array2"; do
echo "$dirname"
done
echo
for dirname in "${array2[#]}"; do
echo "$dirname"
done
rmdir temp/aaa
rmdir temp/bbb
rmdir temp/ccc
rmdir temp
Possible first line of every Bash script/session:
say() { for line in "${#}" ; do printf "%s\n" "${line}" ; done ; }
Use e.g.:
$ aa=( 7 -4 -e ) ; say "${aa[#]}"
7
-4
-e
May consider: echo interprets -e as option here
Single line looping,
declare -a listOfNames=('db_a' 'db_b' 'db_c')
for databaseName in ${listOfNames[#]}; do echo $databaseName; done;
you will get an output like this,
db_a
db_b
db_c
I loop through an array of my projects for a git pull update:
#!/bin/sh
projects="
web
ios
android
"
for project in $projects do
cd $HOME/develop/$project && git pull
end