In the following bash function I would like a new variable called PASS to be created on the first $2 occurrence and then have the new $PASS variable to be tested in the second $2 occurrence.
function ask() {
while read -s -p "Type your $1 and press enter: " $2 && [[ -z "${$2// }" ]]; do
echoboldred -e "\n${1^} can't be blank."
done
}
ask password PASS
The problem is the ${$2// }.
To perform the // on the variable whose name is in $2,
the correct syntax is ${!2// }.
while read -s -p "Type your $1 and press enter: " "$2" && [[ -z "${!2// }" ]]; do
You can also use nameref declared with local -n instead of parameter indirection, it might make your code more readable:
ask() {
local -n foo=$2
while read -srp "Type your $1 and press enter: " foo && ! [[ $foo ]]; do
printf -- "\n%s can't be blank.\n" "${1^}"
done
}
ask password pass
Don't declare your functions with the function keyword and it's also advisable to use -r option with read in case your password has backslashes in it:
-r do not allow backslashes to escape any characters
Related
I am trying to search how to pass parameters in a Bash function, but what comes up is always how to pass parameter from the command line.
I would like to pass parameters within my script. I tried:
myBackupFunction("..", "...", "xx")
function myBackupFunction($directory, $options, $rootPassword) {
...
}
But the syntax is not correct. How can I pass a parameter to my function?
There are two typical ways of declaring a function. I prefer the second approach.
function function_name {
command...
}
or
function_name () {
command...
}
To call a function with arguments:
function_name "$arg1" "$arg2"
The function refers to passed arguments by their position (not by name), that is $1, $2, and so forth. $0 is the name of the script itself.
Example:
function_name () {
echo "Parameter #1 is $1"
}
Also, you need to call your function after it is declared.
#!/usr/bin/env sh
foo 1 # this will fail because foo has not been declared yet.
foo() {
echo "Parameter #1 is $1"
}
foo 2 # this will work.
Output:
./myScript.sh: line 2: foo: command not found
Parameter #1 is 2
Reference: Advanced Bash-Scripting Guide.
Knowledge of high level programming languages (C/C++, Java, PHP, Python, Perl, etc.) would suggest to the layman that Bourne Again Shell (Bash) functions should work like they do in those other languages.
Instead, Bash functions work like shell commands and expect arguments to be passed to them in the same way one might pass an option to a shell command (e.g. ls -l). In effect, function arguments in Bash are treated as positional parameters ($1, $2..$9, ${10}, ${11}, and so on). This is no surprise considering how getopts works. Do not use parentheses to call a function in Bash.
(Note: I happen to be working on OpenSolaris at the moment.)
# Bash style declaration for all you PHP/JavaScript junkies. :-)
# $1 is the directory to archive
# $2 is the name of the tar and zipped file when all is done.
function backupWebRoot ()
{
tar -cvf - "$1" | zip -n .jpg:.gif:.png "$2" - 2>> $errorlog &&
echo -e "\nTarball created!\n"
}
# sh style declaration for the purist in you. ;-)
# $1 is the directory to archive
# $2 is the name of the tar and zipped file when all is done.
backupWebRoot ()
{
tar -cvf - "$1" | zip -n .jpg:.gif:.png "$2" - 2>> $errorlog &&
echo -e "\nTarball created!\n"
}
# In the actual shell script
# $0 $1 $2
backupWebRoot ~/public/www/ webSite.tar.zip
Want to use names for variables? Just do something this.
local filename=$1 # The keyword declare can be used, but local is semantically more specific.
Be careful, though. If an argument to a function has a space in it, you may want to do this instead! Otherwise, $1 might not be what you think it is.
local filename="$1" # Just to be on the safe side. Although, if $1 was an integer, then what? Is that even possible? Humm.
Want to pass an array to a function by value?
callingSomeFunction "${someArray[#]}" # Expands to all array elements.
Inside the function, handle the arguments like this.
function callingSomeFunction ()
{
for value in "$#" # You want to use "$#" here, not "$*" !!!!!
do
:
done
}
Need to pass a value and an array, but still use "$#" inside the function?
function linearSearch ()
{
local myVar="$1"
shift 1 # Removes $1 from the parameter list
for value in "$#" # Represents the remaining parameters.
do
if [[ $value == $myVar ]]
then
echo -e "Found it!\t... after a while."
return 0
fi
done
return 1
}
linearSearch $someStringValue "${someArray[#]}"
In Bash 4.3 and above, you can pass an array to a function by reference by defining the parameter of a function with the -n option.
function callingSomeFunction ()
{
local -n someArray=$1 # also ${1:?} to make the parameter mandatory.
for value in "${someArray[#]}" # Nice!
do
:
done
}
callingSomeFunction myArray # No $ in front of the argument. You pass by name, not expansion / value.
If you prefer named parameters, it's possible (with a few tricks) to actually pass named parameters to functions (also makes it possible to pass arrays and references).
The method I developed allows you to define named parameters passed to a function like this:
function example { args : string firstName , string lastName , integer age } {
echo "My name is ${firstName} ${lastName} and I am ${age} years old."
}
You can also annotate arguments as #required or #readonly, create ...rest arguments, create arrays from sequential arguments (using e.g. string[4]) and optionally list the arguments in multiple lines:
function example {
args
: #required string firstName
: string lastName
: integer age
: string[] ...favoriteHobbies
echo "My name is ${firstName} ${lastName} and I am ${age} years old."
echo "My favorite hobbies include: ${favoriteHobbies[*]}"
}
In other words, not only you can call your parameters by their names (which makes up for a more readable core), you can actually pass arrays (and references to variables - this feature works only in Bash 4.3 though)! Plus, the mapped variables are all in the local scope, just as $1 (and others).
The code that makes this work is pretty light and works both in Bash 3 and Bash 4 (these are the only versions I've tested it with). If you're interested in more tricks like this that make developing with bash much nicer and easier, you can take a look at my Bash Infinity Framework, the code below is available as one of its functionalities.
shopt -s expand_aliases
function assignTrap {
local evalString
local -i paramIndex=${__paramIndex-0}
local initialCommand="${1-}"
if [[ "$initialCommand" != ":" ]]
then
echo "trap - DEBUG; eval \"${__previousTrap}\"; unset __previousTrap; unset __paramIndex;"
return
fi
while [[ "${1-}" == "," || "${1-}" == "${initialCommand}" ]] || [[ "${##}" -gt 0 && "$paramIndex" -eq 0 ]]
do
shift # First colon ":" or next parameter's comma ","
paramIndex+=1
local -a decorators=()
while [[ "${1-}" == "#"* ]]
do
decorators+=( "$1" )
shift
done
local declaration=
local wrapLeft='"'
local wrapRight='"'
local nextType="$1"
local length=1
case ${nextType} in
string | boolean) declaration="local " ;;
integer) declaration="local -i" ;;
reference) declaration="local -n" ;;
arrayDeclaration) declaration="local -a"; wrapLeft= ; wrapRight= ;;
assocDeclaration) declaration="local -A"; wrapLeft= ; wrapRight= ;;
"string["*"]") declaration="local -a"; length="${nextType//[a-z\[\]]}" ;;
"integer["*"]") declaration="local -ai"; length="${nextType//[a-z\[\]]}" ;;
esac
if [[ "${declaration}" != "" ]]
then
shift
local nextName="$1"
for decorator in "${decorators[#]}"
do
case ${decorator} in
#readonly) declaration+="r" ;;
#required) evalString+="[[ ! -z \$${paramIndex} ]] || echo \"Parameter '$nextName' ($nextType) is marked as required by '${FUNCNAME[1]}' function.\"; " >&2 ;;
#global) declaration+="g" ;;
esac
done
local paramRange="$paramIndex"
if [[ -z "$length" ]]
then
# ...rest
paramRange="{#:$paramIndex}"
# trim leading ...
nextName="${nextName//\./}"
if [[ "${##}" -gt 1 ]]
then
echo "Unexpected arguments after a rest array ($nextName) in '${FUNCNAME[1]}' function." >&2
fi
elif [[ "$length" -gt 1 ]]
then
paramRange="{#:$paramIndex:$length}"
paramIndex+=$((length - 1))
fi
evalString+="${declaration} ${nextName}=${wrapLeft}\$${paramRange}${wrapRight}; "
# Continue to the next parameter:
shift
fi
done
echo "${evalString} local -i __paramIndex=${paramIndex};"
}
alias args='local __previousTrap=$(trap -p DEBUG); trap "eval \"\$(assignTrap \$BASH_COMMAND)\";" DEBUG;'
Drop the parentheses and commas:
myBackupFunction ".." "..." "xx"
And the function should look like this:
function myBackupFunction() {
# Here $1 is the first parameter, $2 the second, etc.
}
A simple example that will clear both during executing script or inside script while calling a function.
#!/bin/bash
echo "parameterized function example"
function print_param_value(){
value1="${1}" # $1 represent first argument
value2="${2}" # $2 represent second argument
echo "param 1 is ${value1}" # As string
echo "param 2 is ${value2}"
sum=$(($value1+$value2)) # Process them as number
echo "The sum of two value is ${sum}"
}
print_param_value "6" "4" # Space-separated value
# You can also pass parameters during executing the script
print_param_value "$1" "$2" # Parameter $1 and $2 during execution
# Suppose our script name is "param_example".
# Call it like this:
#
# ./param_example 5 5
#
# Now the parameters will be $1=5 and $2=5
It takes two numbers from the user, feeds them to the function called add (in the very last line of the code), and add will sum them up and print them.
#!/bin/bash
read -p "Enter the first value: " x
read -p "Enter the second value: " y
add(){
arg1=$1 # arg1 gets to be the first assigned argument (note there are no spaces)
arg2=$2 # arg2 gets to be the second assigned argument (note there are no spaces)
echo $(($arg1 + $arg2))
}
add x y # Feeding the arguments
Another way to pass named parameters to Bash... is passing by reference. This is supported as of Bash 4.0
#!/bin/bash
function myBackupFunction(){ # directory options destination filename
local directory="$1" options="$2" destination="$3" filename="$4";
echo "tar cz ${!options} ${!directory} | ssh root#backupserver \"cat > /mnt/${!destination}/${!filename}.tgz\"";
}
declare -A backup=([directory]=".." [options]="..." [destination]="backups" [filename]="backup" );
myBackupFunction backup[directory] backup[options] backup[destination] backup[filename];
An alternative syntax for Bash 4.3 is using a nameref.
Although the nameref is a lot more convenient in that it seamlessly dereferences, some older supported distros still ship an older version, so I won't recommend it quite yet.
There is a bunch of variables to assign value. I was able to do it in a stupid way by copy-pasting the same piece of code, and then change the part that is different.
For example, I want to do the following:
export country="US"
export city="LA"
The stupid way, with a user-input interface, is:
printf "\nPlease assign country$ \n" ;
if [[ $country == nil ]] ; then
printf "Current value is nil\n"
else
printf "Current value is: $country\n"
fi ;
printf "country: " ;
read -e -i $country country_
export country=$country_
And for city, I just search-replace "country" with "city" and past the code, which is stupid, but works.
Now, I want to improve the readability, and also maintainability, of the code, buy putting the variable names in a list and then iterate over this list.
The half-worked-out code, after googling is:
declare -a var_list=("country" "city")
for var in ${var_list[*]}
do
printf "\nPlease assign $var \n" ;
if [[ ${!var} == nil ]] ; then
printf "Current value is nil\n"
else
printf "Current value is: ${!var}\n"
fi ;
printf "${bold}$var: ${normal}" ;
read -e -i ${!var} {$var_}
export $var={$var_}
done
The following 2 lines of codes are still not correct to do what I want them to do:
read -e -i ${!var} {$var_}
export $var={$var_}
I would like to get some help on that.
Make a function from it and pass variable name to it:
get() {
# descriptive variable names
local var previousvalue
var="$1"
previousvalue="${!1}"
# superfluous, servers as a documentation
# The string "$1" should be a global variable
declare -g "$var"
# Asking the real questions:
printf "\nPlease assign $var \n"
printf "Current value is '$previousvalue'\n"
read -e -p "$1: " -i "$previousvalue" "$var"
}
declare -a var_list=("country" "city")
for i in "${var_list[#]}"; do # or just `for i in country city; do`
get "$i"
done
echo
echo "country=$country"
echo "city=$city"
example exeuction:
Please assign country
Current value is ''
country: Poland
Please assign city
Current value is ''
city: Warsaw
country=Poland
city=Warsaw
Notes:
Don't use for var in ${var_list[*]}, it will improperly handle array elements with spaces inside them. Do for var in "${var_list[#]}". The "${...[#]}" will properly quote and pass all variables.
The export $var={$var_} line exports the variable named after expansion $var to the string consisting of { the expansion of var_ variable and }. I guess you don't want to include the { } in the value. I guess you wanted to write "${var}_" or "${var_}" - the { have to be after $.
I suggest you avoid resorting to variable indirection and use a function instead :
display_and_read() {
local item_type="$1" previous_value="$2"
printf "\nPlease assign $item_type$ \n" ;
if [[ $previous_value == nil ]] ; then
printf "Current value is nil\n"
else
printf "Current value is: $previous_value\n"
fi ;
printf "$item_type: " ;
}
display_and_read "country" "$country"
read -e -i $country country_
export country=$country_
display_and_read "city" "$city"
read -e -i $city city_
export city=$city_
This question already has answers here:
Dynamic variable names in Bash
(19 answers)
How to use a variable's value as another variable's name in bash [duplicate]
(6 answers)
Closed 5 years ago.
In my bash scripts, I often prompt users for y/n answers. Since I often use this several times in a single script, I'd like to have a function that checks if the user input is some variant of Yes / No, and then cleans this answer to "y" or "n". Something like this:
yesno(){
temp=""
if [[ "$1" =~ ^([Yy](es|ES)?|[Nn][Oo]?)$ ]] ; then
temp=$(echo "$1" | tr '[:upper:]' '[:lower:]' | sed 's/es//g' | sed 's/no//g')
break
else
echo "$1 is not a valid answer."
fi
}
I then would like to use the function as follows:
while read -p "Do you want to do this? " confirm; do # Here the user types "YES"
yesno $confirm
done
if [[ $confirm == "y" ]]; then
[do something]
fi
Basically, I want to change the value of the first argument to the value of $confirm, so that when I exit the yesno function, $confirm is either "y" or "n".
I tried using set -- "$temp" within the yesnofunction, but I can't get it to work.
You could do it by outputting the new value and overwriting the variable in the caller.
yesno() {
if [[ "$1" =~ ^([Yy](es|ES)?|[Nn][Oo]?)$ ]] ; then
local answer=${1,,}
echo "${answer::1}"
else
echo "$1 is not a valid answer." >&2
echo "$1" # output the original value
return 1 # indicate failure in case the caller cares
fi
}
confirm=$(yesno "$confirm")
However, I'd recommend a more direct approach: have the function do the prompting and looping. Move all of that repeated logic inside. Then the call site is super simple.
confirm() {
local prompt=$1
local reply
while true; do
read -p "$prompt" reply
case ${reply,,} in
y*) return 0;;
n*) return 1;;
*) echo "$reply is not a valid answer." >&2;;
esac
done
}
if confirm "Do you want to do this? "; then
# Do it.
else
# Don't do it.
fi
(${reply,,} is a bash-ism that converts $reply to lowercase.)
You could use the nameref attribute of Bash (requires Bash 4.3 or newer) as follows:
#!/bin/bash
yesno () {
# Declare arg as reference to argument provided
declare -n arg=$1
local re1='(y)(es)?'
local re2='(n)o?'
# Set to empty and return if no regex matches
[[ ${arg,,} =~ $re1 ]] || [[ ${arg,,} =~ $re2 ]] || { arg= && return; }
# Assign "y" or "n" to reference
arg=${BASH_REMATCH[1]}
}
while read -p "Prompt: " confirm; do
yesno confirm
echo "$confirm"
done
A sample test run looks like this:
Prompt: YES
y
Prompt: nOoOoOo
n
Prompt: abc
Prompt:
The expressions are anchored at the start, so yessss etc. all count as well. If this is not desired, an end anchor ($) can be added.
If neither expression matches, the string is set to empty.
I have a function in bash that get param a string, for example:
MYSQL_DATABASE then I want in my file to create a var named VAR_MYSQL_DATABASE but I can`t get the value.
create_var()
{
read -p "Enter $1 : " VAR_$1
printf VAR_$1 // print VAR_MYSQL_DATABASE_NAME instead what I typed, so how do I get the value?
if [[ -z VAR_$1 ]]; then
printf '%s\n' "No input entered. Enter $1"
create_entry $1
fi
}
create_var "MYSQL_DATABASE_NAME"
Use the declare built-in in bash,
name="MYSQL_DATABASE"
declare VAR_${name}="Some junk string"
printf "%s\n" "${VAR_MYSQL_DATABASE}"
Some junk string
With the above logic, you can modify how your name variable is controlled, either present locally. If it is passed as argument from a function/command-line do
declare VAR_${1}="Your string value here"
Perhaps you want to achieve something like this,
create_var()
{
read -p "Enter value: " value
declare -g VAR_$1="$value"
dynamVar="VAR_$1"
if [[ -z "${!dynamVar}" ]]; then
printf '%s\n' "No input entered. Enter $1"
create_entry $1
fi
}
So, here we are creating the dynamic variable using the declare built-in and with the dynamic part VAR_$1 cannot be referenced directly as normal variables, hence using indirect expansion {!variable} to see if the created variable is available.
Try the following :
#!/bin/bash
create_var() {
declare -g VAR_$1
ref=VAR_$1
read -p "Enter $1: " "VAR_$1"
echo "inside : ${!ref}"
}
create_var "MYSQL_DATABASE_NAME"
echo "output : $VAR_MYSQL_DATABASE_NAME"
declare -g will make sure the variable exists outside of the function scope, and "VAR_$1" is used to dynamically create the variable names.
Output :
Enter MYSQL_DATABASE_NAME: Apple
inside : Apple
output : Apple
You can use the printf function with the -v option to "print" to a variable name.
create_var()
{
while : ; do
IFS= read -r -p "Enter $1 : " value
if [[ -n $value ]]; then
printf -v "VAR_$1" '%s' "$value"
return
fi
printf 'No input entered. Enter %s\n' "$1"
done
}
(I've rewritten your function with a loop to avoid what appeared to be an attempt at recursion.)
I am trying to search how to pass parameters in a Bash function, but what comes up is always how to pass parameter from the command line.
I would like to pass parameters within my script. I tried:
myBackupFunction("..", "...", "xx")
function myBackupFunction($directory, $options, $rootPassword) {
...
}
But the syntax is not correct. How can I pass a parameter to my function?
There are two typical ways of declaring a function. I prefer the second approach.
function function_name {
command...
}
or
function_name () {
command...
}
To call a function with arguments:
function_name "$arg1" "$arg2"
The function refers to passed arguments by their position (not by name), that is $1, $2, and so forth. $0 is the name of the script itself.
Example:
function_name () {
echo "Parameter #1 is $1"
}
Also, you need to call your function after it is declared.
#!/usr/bin/env sh
foo 1 # this will fail because foo has not been declared yet.
foo() {
echo "Parameter #1 is $1"
}
foo 2 # this will work.
Output:
./myScript.sh: line 2: foo: command not found
Parameter #1 is 2
Reference: Advanced Bash-Scripting Guide.
Knowledge of high level programming languages (C/C++, Java, PHP, Python, Perl, etc.) would suggest to the layman that Bourne Again Shell (Bash) functions should work like they do in those other languages.
Instead, Bash functions work like shell commands and expect arguments to be passed to them in the same way one might pass an option to a shell command (e.g. ls -l). In effect, function arguments in Bash are treated as positional parameters ($1, $2..$9, ${10}, ${11}, and so on). This is no surprise considering how getopts works. Do not use parentheses to call a function in Bash.
(Note: I happen to be working on OpenSolaris at the moment.)
# Bash style declaration for all you PHP/JavaScript junkies. :-)
# $1 is the directory to archive
# $2 is the name of the tar and zipped file when all is done.
function backupWebRoot ()
{
tar -cvf - "$1" | zip -n .jpg:.gif:.png "$2" - 2>> $errorlog &&
echo -e "\nTarball created!\n"
}
# sh style declaration for the purist in you. ;-)
# $1 is the directory to archive
# $2 is the name of the tar and zipped file when all is done.
backupWebRoot ()
{
tar -cvf - "$1" | zip -n .jpg:.gif:.png "$2" - 2>> $errorlog &&
echo -e "\nTarball created!\n"
}
# In the actual shell script
# $0 $1 $2
backupWebRoot ~/public/www/ webSite.tar.zip
Want to use names for variables? Just do something this.
local filename=$1 # The keyword declare can be used, but local is semantically more specific.
Be careful, though. If an argument to a function has a space in it, you may want to do this instead! Otherwise, $1 might not be what you think it is.
local filename="$1" # Just to be on the safe side. Although, if $1 was an integer, then what? Is that even possible? Humm.
Want to pass an array to a function by value?
callingSomeFunction "${someArray[#]}" # Expands to all array elements.
Inside the function, handle the arguments like this.
function callingSomeFunction ()
{
for value in "$#" # You want to use "$#" here, not "$*" !!!!!
do
:
done
}
Need to pass a value and an array, but still use "$#" inside the function?
function linearSearch ()
{
local myVar="$1"
shift 1 # Removes $1 from the parameter list
for value in "$#" # Represents the remaining parameters.
do
if [[ $value == $myVar ]]
then
echo -e "Found it!\t... after a while."
return 0
fi
done
return 1
}
linearSearch $someStringValue "${someArray[#]}"
In Bash 4.3 and above, you can pass an array to a function by reference by defining the parameter of a function with the -n option.
function callingSomeFunction ()
{
local -n someArray=$1 # also ${1:?} to make the parameter mandatory.
for value in "${someArray[#]}" # Nice!
do
:
done
}
callingSomeFunction myArray # No $ in front of the argument. You pass by name, not expansion / value.
If you prefer named parameters, it's possible (with a few tricks) to actually pass named parameters to functions (also makes it possible to pass arrays and references).
The method I developed allows you to define named parameters passed to a function like this:
function example { args : string firstName , string lastName , integer age } {
echo "My name is ${firstName} ${lastName} and I am ${age} years old."
}
You can also annotate arguments as #required or #readonly, create ...rest arguments, create arrays from sequential arguments (using e.g. string[4]) and optionally list the arguments in multiple lines:
function example {
args
: #required string firstName
: string lastName
: integer age
: string[] ...favoriteHobbies
echo "My name is ${firstName} ${lastName} and I am ${age} years old."
echo "My favorite hobbies include: ${favoriteHobbies[*]}"
}
In other words, not only you can call your parameters by their names (which makes up for a more readable core), you can actually pass arrays (and references to variables - this feature works only in Bash 4.3 though)! Plus, the mapped variables are all in the local scope, just as $1 (and others).
The code that makes this work is pretty light and works both in Bash 3 and Bash 4 (these are the only versions I've tested it with). If you're interested in more tricks like this that make developing with bash much nicer and easier, you can take a look at my Bash Infinity Framework, the code below is available as one of its functionalities.
shopt -s expand_aliases
function assignTrap {
local evalString
local -i paramIndex=${__paramIndex-0}
local initialCommand="${1-}"
if [[ "$initialCommand" != ":" ]]
then
echo "trap - DEBUG; eval \"${__previousTrap}\"; unset __previousTrap; unset __paramIndex;"
return
fi
while [[ "${1-}" == "," || "${1-}" == "${initialCommand}" ]] || [[ "${##}" -gt 0 && "$paramIndex" -eq 0 ]]
do
shift # First colon ":" or next parameter's comma ","
paramIndex+=1
local -a decorators=()
while [[ "${1-}" == "#"* ]]
do
decorators+=( "$1" )
shift
done
local declaration=
local wrapLeft='"'
local wrapRight='"'
local nextType="$1"
local length=1
case ${nextType} in
string | boolean) declaration="local " ;;
integer) declaration="local -i" ;;
reference) declaration="local -n" ;;
arrayDeclaration) declaration="local -a"; wrapLeft= ; wrapRight= ;;
assocDeclaration) declaration="local -A"; wrapLeft= ; wrapRight= ;;
"string["*"]") declaration="local -a"; length="${nextType//[a-z\[\]]}" ;;
"integer["*"]") declaration="local -ai"; length="${nextType//[a-z\[\]]}" ;;
esac
if [[ "${declaration}" != "" ]]
then
shift
local nextName="$1"
for decorator in "${decorators[#]}"
do
case ${decorator} in
#readonly) declaration+="r" ;;
#required) evalString+="[[ ! -z \$${paramIndex} ]] || echo \"Parameter '$nextName' ($nextType) is marked as required by '${FUNCNAME[1]}' function.\"; " >&2 ;;
#global) declaration+="g" ;;
esac
done
local paramRange="$paramIndex"
if [[ -z "$length" ]]
then
# ...rest
paramRange="{#:$paramIndex}"
# trim leading ...
nextName="${nextName//\./}"
if [[ "${##}" -gt 1 ]]
then
echo "Unexpected arguments after a rest array ($nextName) in '${FUNCNAME[1]}' function." >&2
fi
elif [[ "$length" -gt 1 ]]
then
paramRange="{#:$paramIndex:$length}"
paramIndex+=$((length - 1))
fi
evalString+="${declaration} ${nextName}=${wrapLeft}\$${paramRange}${wrapRight}; "
# Continue to the next parameter:
shift
fi
done
echo "${evalString} local -i __paramIndex=${paramIndex};"
}
alias args='local __previousTrap=$(trap -p DEBUG); trap "eval \"\$(assignTrap \$BASH_COMMAND)\";" DEBUG;'
Drop the parentheses and commas:
myBackupFunction ".." "..." "xx"
And the function should look like this:
function myBackupFunction() {
# Here $1 is the first parameter, $2 the second, etc.
}
A simple example that will clear both during executing script or inside script while calling a function.
#!/bin/bash
echo "parameterized function example"
function print_param_value(){
value1="${1}" # $1 represent first argument
value2="${2}" # $2 represent second argument
echo "param 1 is ${value1}" # As string
echo "param 2 is ${value2}"
sum=$(($value1+$value2)) # Process them as number
echo "The sum of two value is ${sum}"
}
print_param_value "6" "4" # Space-separated value
# You can also pass parameters during executing the script
print_param_value "$1" "$2" # Parameter $1 and $2 during execution
# Suppose our script name is "param_example".
# Call it like this:
#
# ./param_example 5 5
#
# Now the parameters will be $1=5 and $2=5
It takes two numbers from the user, feeds them to the function called add (in the very last line of the code), and add will sum them up and print them.
#!/bin/bash
read -p "Enter the first value: " x
read -p "Enter the second value: " y
add(){
arg1=$1 # arg1 gets to be the first assigned argument (note there are no spaces)
arg2=$2 # arg2 gets to be the second assigned argument (note there are no spaces)
echo $(($arg1 + $arg2))
}
add x y # Feeding the arguments
Another way to pass named parameters to Bash... is passing by reference. This is supported as of Bash 4.0
#!/bin/bash
function myBackupFunction(){ # directory options destination filename
local directory="$1" options="$2" destination="$3" filename="$4";
echo "tar cz ${!options} ${!directory} | ssh root#backupserver \"cat > /mnt/${!destination}/${!filename}.tgz\"";
}
declare -A backup=([directory]=".." [options]="..." [destination]="backups" [filename]="backup" );
myBackupFunction backup[directory] backup[options] backup[destination] backup[filename];
An alternative syntax for Bash 4.3 is using a nameref.
Although the nameref is a lot more convenient in that it seamlessly dereferences, some older supported distros still ship an older version, so I won't recommend it quite yet.