在脚本中运行时，su -c命令失败

Question

I am trying to issue a unicorn command via a shell script on a digital ocean ubuntu server. The command is:

su - xxx -c cd /home/xxx/apps/app_name && rbenv rehash && rbenv local 2.3.1 && /home/xxx/apps/app_name/bin/unicorn -c /home/xxx/apps/app_name/config/unicorn.rb -E production -D

This command works when issued on the command line but if I put it into a script like this:

#!/bin/sh

USER=xxx

APP_ROOT=/home/xxx/apps/app_name
RBENV_RUBY_VERSION=2.3.1

SET_PATH="cd $APP_ROOT && rbenv rehash && rbenv local $RBENV_RUBY_VERSION"
RAILS_ENV=production
UNICORN="$APP_ROOT/bin/unicorn"
UNICORN_OPTS="-c $APP_ROOT/config/unicorn.rb -E $RAILS_ENV -D"
CMD="$SET_PATH && $UNICORN $UNICORN_OPTS"

su - $USER -c "$CMD"

I get this error: -su: rbenv: command not found

If I remove the quotes around $CMD , I get this error: su: invalid option -- 'E'

Does anyone know how to get around this problem?

Following the comments below, I have amended the script by adding a path to rbenv like this:

RBENV_ROOT="/home/$USER/.rbenv"
SET_PATH="cd $APP_ROOT && $RBENV_ROOT/bin/rbenv rehash && $RBENV_ROOT/bin/rbenv local $RBENV_RUBY_VERSION"

When I run this now I get the following error: -su: cd /home/xxx/apps/app_name && /home/xxx/.rbenv/bin/rbenv rehash && /home/xxx/.rbenv/bin/rbenv local 2.3.1 && /home/xxx/apps/app_name/bin/unicorn /home/xxx/apps/app_name/config/unicorn.rb -E production -D: No such file or directory

Answer 1

The reason you get different results, is that the shell splits the command is actually split into multiply parts:

su - xxx -c cd /home/xxx/apps/app_name 
&& rbenv rehash
&& rbenv local 2.3.1 
&& /home/xxx/apps/app_name/bin/unicorn -c /home/xxx/apps/app_name/config/unicorn.rb -E production -D

For each newline a new command is called in your shell (As your user, not the substituted).

The above means call su with '-' 'xxx' '-c' 'cd' '/home/xxx/apps/app_name' , if that success then call rbenv with 'rehash' , and so on...

And in your script all of these are interpreted as one arguments:

# Terminal:
su - user -c ls && echo 1
# Script
su - user -c 'ls && echo 1'

When all of this is said, it should be clear that your script is doing what it should do, but that rbenv is not in the $PATH set inside su . You can get around this by using the absolute path to rbenv :

su - xxx -c 'cd /home/xxx/apps/app_name && /path/to/rbenv ...'

A few things to note: Uppercase variable names are reserved to environment variables , so you should consider using lowercase names. When you don't wrap parameter expansions in double quotes they will undergo word splitting and globbing .

Answer 2

In your case the su command is applied only to the cd command.

Shell will split your command to following commands and evaluate each of them separately and use their return code to (partially) evaluate the && expression:

su - xxx -c cd /home/xxx/apps/app_name
rbenv rehash
rbenv local 2.3.1
/home/xxx/apps/app_name/bin/unicorn -c /home/xxx/apps/app_name/config/unicorn.rb -E production -D

So when we draw an evaluation tree, it will look like this:

shell
 `-- &&
     |-- su
     |   `-- shell
     |       `-- cd
     |-- rbenv
     |-- rbenv
     `-- unicorn

So to apply su to whole thing (as you want) wrap it in the quotes:

su - xxx -c 'cd /home... && rbenv ... && ...'

So when we draw an evaluation tree of the fixed command, it will look like this:

shell
 `-- su
     `-- shell
         `-- &&
             |-- cd
             |-- rbenv
             |-- rbenv
             `-- unicorn