CODEWITHSUNDEEP
bashshellsed
jangorecki
jangorecki

Reputation: 16697

substitute env var in character string argument passed from command line

I can find plenty of answers which uses echo, pipes | and sed for that purpose, but I would like to avoid them. So looking for some direct substitution.

I would like to define env var and reuse it inside the character string passed to application command line argument, i.e. Rscript -e '...'.
Below is what I've tried without success.

Rscript -e 'cat("hello\n")'
#hello
export ASD="HELLO!"
Rscript -e 'cat("$ASD\n")'
#$ASD
Rscript -e 'cat("${ASD}\n")'
#${ASD}
Rscript -e 'cat("$(ASD)\n")'
#$(ASD)

I don't want to use echo and | pipes as my actual -e argument to application is much more complex.

Upvotes: 0

Views: 82

Answers (2)

ghoti
ghoti

Reputation: 46836

In addition to fun with quotes, you might be able to use positional parameters. Your question fails to provide a Minimal, Complete, Verifiable Example so I can't be sure this is in line with your needs.

bash-4.3$ bash -c 'set -; echo "${0^^} ... ${1/o/0}"' hello world
HELLO ... w0rld

Upvotes: 1

Michael Vehrs
Michael Vehrs

Reputation: 3363

$ date > filename
$ export filename=len
$ cat 'fi'"$filename"'ame'
Sun Apr 17 16:20:20 CEST 2016

Upvotes: 0

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