Bash script to read from a file and execute commands

Question

I want a bash script that reads the java arguments from a file and executes java with them

jvm_arguments=$(cat jvm-args)
exec java $jvm_arguments

The problem is that it does not work very well with this jvm-args file:

-Xms128m -Xmx512m -Dhostname=$(hostname)

The command hostname is not executed and replaced.

How can I get the hostname command executed? so that I get:

exec java -Xms128m -Xmx512m -Dhostname=MyMachine

Thanks.

Be careful with this. There is a reason why bash does not do this sort of thing automatically: it can be a gaping security hole. — John1024
– John1024, Commented Nov 5, 2014 at 22:55
InetAddress.getLocalHost().getHostName() might be another solution (download.java.net/jdk7/archive/b123/docs/api/java/net/…) — Vytenis Bivainis
– Vytenis Bivainis, Commented Nov 5, 2014 at 23:22

jakub.petr · Accepted Answer · 2014-11-05 22:51:39Z

2

Use eval to evaluate your runtime variables. Like this (not tested):

jvm_arguments=$(cat jvm-args)
eval java $jvm_arguments

answered Nov 5, 2014 at 22:51

jakub.petr

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1 Comment

If bash only, jvm_arguments=$(< jvm-args) will cause the shell to read the file rather than needing another cat process.

Vytenis Bivainis · Accepted Answer · 2014-11-05 23:26:19Z

1

Store the whole command in file, for example, run.sh

exec java -Xms128m -Xmx512m -Dhostname=$(hostname) ...

If you want current bash process to be terminated, call with . run.sh

answered Nov 5, 2014 at 23:26

Vytenis Bivainis

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