mjhjmtu

I am writing a shell function which makes an external API call via cURL (the external API syntax isn't under my control). I've approached it like this (simplified):

#!/bin/sh

template_get_entry='get_entry:%s'
template_set_entry='set_entry:%s=%s'

curlheaders='-H stuff'
curluri="https://www.domain.com:1234/api.php"

# make an API call to get entry "foo"
call_api "$template_get_entry" "foo"

# make an API call to set entry "foo" to "bar"
call_api "$template_set_entry" "foo" "bar"

call_api() 

 apicmd="$( printf "$1" "$2" "$3" )"
 result="$( eval "/usr/local/bin/curl" "$curlheaders" "-d" "$apicmd" "$curluri" )"
 retcode="$?"

 .....stuff.....

There are 2 problems with this code.

First, the number of args is variable. If the line defining apicmd is called with less than the maximal number of args, printf interprets any excess commands as extra instances of printing the format string, to be appended. I can't see the correct way to work around this.

Second, because I've used eval, this creates a knockon problem with eval, in that retcode will surely pick up the return code from eval and not from curl, and I don't know the right way to prevent/fix that.

How should I do something like this, which needs a variable number of args?

You could try to fill the format strings with zero length specifiers up to the maximum expected parameter count:

template_get_entry='get_entry:%s %0.0s'

What you could do is to get the format string argument, shift it off the argument list and then use $@:

call_api () 
 fmt=$1
 shift

 apicmd=$( printf "$fmt" "$@" )

 # ...