How do I assign the output of a command to a variable within a loop in bash?


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Top Forums UNIX for Beginners Questions & Answers How do I assign the output of a command to a variable within a loop in bash?
# 8  
Quote:
Originally Posted by RudiC
What does <path> stand for? Does the readlink result have 7+ / separated fields?
<path> = path to the symbolic link.
-f7 = relates to the version which is 7th field in the above path.

The output of the command is 1.0.1

Last edited by rbatte1; 04-16-2019 at 07:03 AM.. Reason: Added ICODE tags
# 9  
By "within a loop" do you happen to mean "behind a pipe?" also known as "inside a subshell"? That will not work. Variables inside a subshell do not get communicated to outside the subshell.
# 10  
Quote:
Originally Posted by Corona688
By "within a loop" do you happen to mean "behind a pipe?" also known as "inside a subshell"? That will not work. Variables inside a subshell do not get communicated to outside the subshell.
In which case is there a possibility to evaluate the output of the command to another variable.
eg.

Code:
if ( $(readlink -f <path> | cut -d '/' -f7)" == "$ver"); then


Last edited by rbatte1; 04-16-2019 at 07:04 AM.. Reason: Changed ICODE tags to CODE tags
# 11  
Please show us your entire script instead of showing us one line at a time.

It seems highly likely that you are setting the variable you want inside a sub-shell and that makes the assigned value invisible outside of that sub-shell. But we can't know that until we can see all of your code.
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# 12  
I think the main problem is shown in post#3: the
Code:
readlink -f <path> | cut -d / -f 7

gives an empty string.
(A subshell and/or a wrong assignment would cause additional problems of course.)
If the question is for a better debugging, then I suggest to repeat the readlink -f <path> command without a following pipe. Maybe framed by some "debug" text:
Code:
echo "debug: -->$(readlink -f <path>)<--"

# 13  
Quote:
Originally Posted by sankasu
In which case is there a possibility to evaluate the output of the command to another variable.
If your loop is behind a pipe, that would mean stuffing your entire loop inside $( ). Or storing the result in a temporary file.

This is just guessing though. This is a really common problem which we can't rule out without seeing more of your code.

Last edited by Corona688; 04-16-2019 at 05:03 PM..
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