I am trying to read Xcode build settings via shell script, i.e. if there is a build setting called PRODUCT_NAME, I read its value by writing echo ${PRODUCT_NAME} in shell script.
Now, I get this PRODUCT_NAME in an array, lets call myArr having just one element PRODUCT_NAME. I loop over that array as
for i in "${myarr[#]}"
do
:
echo $i
done
echo $i would simply output PRODUCT_NAME. However, I want to write something that would evaluate ${PRODUCT_NAME} and give me results.
I have also tried eval echo $i but that also outputs PRODUCT_NAME only
Solved it by using
echo "${!i}"
The second line gives the output as desired. I have taken this answer from here: How to get a variable value if variable name is stored as string?
As I interpret your problem, You hold the array of variables, and while traversing, you want to use the actual values of the variables.
I tried the below code which is almost similar to which you have written and seems working.
#!/bin/bash
PRODUCT_NAME="Calendar"
PROCUCT_VER="2.3"
PROCUCT_OWNER="Sam"
PRODUCT_DETAILS=( $PRODUCT_NAME $PROCUCT_VER $PROCUCT_OWNER )
for PRODUCT_PROPERTY in "${PRODUCT_DETAILS[#]}"
do
echo "PRODUCT_PROPERTY: $PRODUCT_PROPERTY"
done
Output:
PRODUCT_PROPERTY: Calendar
PRODUCT_PROPERTY: 2.3
PRODUCT_PROPERTY: Sam
Related
I know something like this is possible with DOS but I am not sure how to do it within bash.
I am writing a script that takes some configuration data: source, name, and destination. There will be a variable number of these in the configuration. I need to iterate over each set.
So, for example:
#!/bin/bash
FOLDER_1_SOURCE="/path/one"
FOLDER_1_NAME="one"
FOLDER_1_DESTINATION="one"
FOLDER_2_SOURCE="/path/two two"
FOLDER_2_NAME="two"
FOLDER_2_DESTINATION="here"
FOLDER_3_SOURCE="/something/random"
FOLDER_3_NAME="bravo"
FOLDER_3_DESTINATION="there"
FOLDER_..._SOURCE="/something/random"
FOLDER_..._NAME="bravo"
FOLDER_..._DESTINATION=""
FOLDER_X_SOURCE="/something/random"
FOLDER_X_NAME="bravo"
FOLDER_X_DESTINATION=""
Then I want to iterate over each set and get the SOURCE and NAME values for each set.
I am not stuck on this format. I just don't know how else to do this. The end goal is that I have 1 or more set of variables with source, name, and destination and then I need to iterate over them.
The answer to this type of question is nearly always "use arrays".
declare -a folder_source folder_name folder_dest
folder_source[1]="/path/one"
folder_name[1]="one"
folder_dest[1]="one"
folder_source[2]="/path/two two"
folder_name[2]="two"
folder_dest[2]="here"
folder_source[3]="/something/random"
folder_name[3]="bravo"
folder_dest[3]="there"
folder_source[4]="/something/random"
folder_name[4]="bravo"
folder_dest[4]=""
for((i=1; i<=${#folder_source[#]}; ++i)); do
echo "$i source:" "${folder_source[$i]}"
echo "$i name:" "${folder_name[$i]}"
echo "$i destination:" "${folder_dest[$i]}"
done
Demo: https://ideone.com/gZn0wH
Bash array indices are zero-based, but we just leave the zeroth slot unused here for convenience.
Tangentially, avoid upper case for your private variables.
AFIK bash does not have a facility to list all variables. A workaround - which also would mimic what is going on in DOS - is to use environment variables and restrict your search to those. In this case, you could do a
printenv|grep ^FOLDER||cut -d = -f 1
This is the same as doing in Windows CMD shell a
SET FOLDER
I have a config file something like below.
_ispip=$_octet.129
_octet=10.89.2
_rxpip=$_octet.132
And when i try to echo the value its not printing the full values for the 1st variable. Is there a easy way to fix this?
# source test.cfg
# echo $_ispip
.129
# echo $_octet
10.89.2
# echo $_rxpip
10.89.2.132
bash doesn't have lazy evaluation, it will try to replace $_octet when you refer to it. If you do this before the assignment, you get an empty string.
You need to put the _octet assignment before _ispip.
_octet=10.89.2
_ispip=$_octet.129
_rxpip=$_octet.132
I have some code that creates a variable of some name automatically and assigns some value to it. The code is something like the following:
myVariableName="zappo"
eval "${myVariableName}=zappo_value"
How would I access the value of this variable using the automatically generated name of the variable? So, I'm looking for some code a bit like the following (but working):
eval "echo ${${myVariableName}}"
(... which may be used in something such as myVariableValue="$(eval "echo ${${myVariableName}}")"...).
Thanks muchly for any assistance
If you think this approach is madness and want offer more general advice, the general idea I'm working on is having variables defined in functions in a library with such names as ${usage} and ${prerequisiteFunctions}. These variables that are defined within functions would be accessed by an interrogation function that can, for instance, ensure that prerequisites etc. are installed. So a loop within this interrogation function is something like this:
for currentFunction in ${functionList}; do
echo "function: ${currentFunction}"
${currentFunction} -interrogate # (This puts the function variables into memory.)
currentInterrogationVariables="${interrogationVariables}" # The variable interrogationVariables contains a list of all function variables available for interrogation.
for currentInterrogationVariable in ${currentInterrogationVariables}; do
echo "content of ${currentInterrogationVariable}:"
eval "echo ${${currentInterrogationVariable}}"
done
done
Thanks again for any ideas!
IIRC, indirection in bash is by !, so try ${!myVariableName}
Try:
echo ${!myVariableName}
It will echo the variable who's name is contained in $myVariableName
For example:
#!/bin/bash
VAR1="ONE"
VAR2="TWO"
VARx="VAR1"
echo ${VARx} # prints "VAR1"
echo ${!VARx} # prints "ONE"
I have one loop that creates a group of variables like DISK1, DISK2... where the number at the end of the variable name gets created by the loop and then loaded with a path to a device name. Now I want to use those variables in another loop to execute a shell command, but the variable doesn't give its contents to the shell command.
for (( counter=1 ; counter<=devcount ; counter++))
do
TEMP="\$DISK$counter"
# $TEMP should hold the variable name of the disk, which holds the device name
# TEMP was only for testing, but still has same problem as $DISK$counter
eval echo $TEMP #This echos correctly
STATD$counter=$(eval "smartctl -H -l error \$DISK$counter" | grep -v "5.41" | grep -v "Joe")
eval echo \$STATD$counter
done
Don't use eval ever, except maybe if there is no other way AND you really know what you are doing.
The STATD$counter=$(...) should give an error. That's not a valid assignment because the string "STATD$counter" is not a valid variable name. What will happen is (using a concrete example, if counter happened to be 3 and your pipeline in the $( ) output "output", bash will only expand that line as far as "STATD3=output" so it will try to find a command named "STATD3=output" and run it. Odds are this is not what you intended.
It sounds like everything you want to do can be accomplished with arrays instead. If you are not familiar with bash arrays take a look at Greg's Wiki, in particular this page or the bash man page to find out how to use them.
For example, in the loop you didn't post in your question: make disk (not DISK: don't use all upper case variable names) an array like so
disk+=( "new value" )
or even
disk[counter]="new value"
Then in the loop in your question, you can make statd an array as well and assign it with values from disk by
statd[counter]="... ${disk[counter]} ..."
It's worth saying again: avoid using eval.
I'm trying to write a shell script to automate a job for me. But i'm currently stuck.
Here's the problem :
I have a variable named var1 (a decreasing number from 25 to 0
and another variable named
var${var1} and this equals to some string.
then when i try to call var${var1} in anywhere in script via echo it fails.
I have tried $[var$var1], ${var$var} and many others but everytime it fails and gives the value of var1 or says operand expected error.
Thanks for your help
It's probably better if you use an array, but you can use indirection:
var25="some string"
var1=25
indirect_var="var$var1"
echo ${!indirect_var} # echoes "some string"
There's only one round of variable expansion, so you can't do it directly. You could use eval:
eval echo \${var$var1}
A better solution is to use an array:
i=5
var[$i]='foo'
echo ${var[$i]}
It sounds like you need bash variable indirection. Take a look at the link below.
http://mywiki.wooledge.org/BashFAQ/006