Shell scripting pass string with variable for later assignment

Question

I am working on Mac OSX and using bash as my shell. I was wondering if there was any way to create a string with some marker in it, that would later be evaluated. Such as:

Str=$(printf '%d is %s' "5" (#some string I don't know yet) )

Later...

some string I don't know yet="something I know now"
echo Str               #produces: 5 is something I know now

I know this in most cases could be remedy by moving the order of where I am placing the variables, but in this case I would like the order to be as is. Or is this not even possible? Thanks for your help.

Carl Norum · Accepted Answer · 2013-06-06 15:06:46Z

4

Sure, just use printf twice. The fist time, escape the %s so that it goes into the string as-is, and the second time use it as the format string.

Str=$(printf '%d is %%s' 5)
New="something I know now"
printf "${Str}" "${New}"

edited Jun 6, 2013 at 15:06

answered Jun 6, 2013 at 15:00

Carl Norum

226k42 gold badges442 silver badges480 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Novice C Over a year ago

Sorry I'm still new to coding in general, do you mean something like this? Str=$(printf '%d is \%s' "5" ) and then later Str=$(printf $Str "$some string I don't know yet"). Ah thank you, your edit has shown me.

Novice C Over a year ago

Thanks again for your help, but is there also a way to pass an arithmetic operators say ** in the string and delay it's evaluation until you get the other variables in there? Say I had Str=5, and I know I wanted to raise it to the power, but I don't know what power yet.

chepner Over a year ago

@NoviceC You should post a new question which demonstrates an example of what you want to delay.

Carl Norum Over a year ago

@NoviceC, yes, you can do that too. Use the same trick, but at the end use $((${Str} ${New})).

Collectives™ on Stack Overflow

Shell scripting pass string with variable for later assignment

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related