0

Consider a script file: ~/project/script.sh

echo "arg 1 $1"  
echo "arg 2 $2"
echo "arg 3 $3"

And elisp file that invokes it using make-process: ~/project/special-mode/special-mode.el

(let* ((script-file  (shell-quote-argument (expand-file-name "~/project/script.sh")))
       (argA          (shell-quote-argument "A"))
       (argB          (shell-quote-argument "B")))
       (make-process
             :name            "special-mode"
             :buffer          "*SPECIAL-MODE*"
             :command         `( "sh" "-c" ,script-file ,argA  ,argB )
             :connection-type 'pipe
             :sentinel   nil)))

Question

The function evaluates but the arguments to the shell script (argA and argB) are never passed. Any idea how to fix this?

Emacs Version

GNU Emacs 28.0.50

1

Your issue is the use of sh -c. When using the -c flag, the next argument is expected to be the full command line that will be expanded by the subshell.

You can try this in a regular shell:

ditto:~% sh -c echo a b c

ditto:~% sh -c 'echo a b c'
a b c
ditto:~%

In the first example, echo is being executed correctly, but because only the first argument after -c is being passed to the subshell, the a b c arguments are lost to echo. In the second example, the entire command line is being passed as a single argument, and thus echo is seeing a b c in the subshell.

So naturally, you have to take this into account in your elisp by passing a single argument to -c:

(let* ((script-file (shell-quote-argument (expand-file-name "/bin/echo")))
       (arg-a       (shell-quote-argument "A"))
       (arg-b       (shell-quote-argument "B")))
  (make-process
   :name            "special-mode"
   :buffer          "*SPECIAL-MODE*"
   :command         `("sh" "-c" ,(concat script-file " " arg-a " " arg-b))
   :connection-type 'pipe
   :sentinel   nil))

I would recommend, however, that instead of using sh -c, just call your binaries directly unless you specifically need to use shell interpretatiton, because it works more naturally and has more predictable outcome.

0

Update:

As pointed out by xuchunyang, adding a shebang line to the script.sh and calling it like an ordinary executable is a much cleaner solution. That is:

#!/bin/bash 
echo "arg 1 $1"  
echo "arg 2 $2"
echo "arg 3 $3"

Old Solution

Removing the -c flag fixed the issue. The -c flag is used to call shell commands in-line(and probably more).

sh -c[-abCefhimnuvx][-o option][+abCefhimnuvx][+o option]command_string
               [command_name [argument...]]

From The Single UNIX ® Specification, Version 2

-c        Read  commands from the command_string operand. Set the value of
          special parameter 0 (see Special Parameters ) from the value  of
          the  command_name operand and the positional parameters ($1, $2,
          and so on) in sequence from the remaining argument operands.  No
          commands shall be read from the standard input.
1
  • You can just execute the program directly without sh by adding a shebang and making it executable. sh -c 'echo $0 $1' app_name arg1 works while sh -c 'echoargs' app_name arg1 doesn't because as you mentioned the former is a inline script, but the later the program echoargs will run in a new process with its own arguments. – xuchunyang May 28 '20 at 8:42

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