Passing multiple quoted arguments to command in bourne shell - command-line

Question

I have a utility (myutil) that I need to pass multiple parameters. The parameters may(will) contain backslashes and spaces and therefore need to be enclosed in single quotes. An example run of this utility is:
myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
I am working on a script which will read these parameters from a multi-line file and feed them into the script. The input file myinput.txt looks like this:
# cat myinput.txt
ONE\APPLE
ONE\PEAR
TWO\RED GRAPE
TWO\TOMATO
I am using the following code to parse the file and execute myutil. The script reads each line as an argument, and encloses it in double quotes (as myutil will expect for values with spaces or special characters) and creates a single variable to hold the entire argument string:
#!/bin/sh
MYCOMMAND=myutil
if [ -f myinput.txt ]; then
ARGSLIST=`cat myinput.txt| sed -e 's/^/"/g' -e 's/$/"/g' | awk '{ printf "%s ", $0 }'`
$MYCOMMAND setOptions "${ARGSLIST}"
printf "%s\n" "$MYCOMMAND setOptions ${ARGSLIST}"
fi
As I might expect, the screen output of this command looks as expected:
myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
However, this is not actually what is being executed based on how myutil would normally process this command. Instead, myutil is processing this as if ALL the arguments were also enclosed within single quotes. Running this debug under sh doesn't reflect this:
+ MYCOMMAND=myutil
+ [ -f myinput.txt ]
+ awk { printf "%s ", $0 }
+ sed -e s/^/"/g -e s/$/"/g
+ cat myinput.txt
+ ARGSLIST="ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
+ myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
+ printf %s\n myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
HOWEVER, running debug under bash seems to show what is really being executed:
+ MYCOMMAND=myutil
+ '[' -f myinput.txt ']'
++ awk '{ printf "%s ", $0 }'
++ sed -e 's/^/"/g' -e 's/$/"/g'
++ cat myinput.txt
+ ARGSLIST='"ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO" '
+ myutil setOptions '"ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO" '
+ printf '%s\n' 'myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO" '
myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
You can see the debug line which shows as:
+ myutil setOptions '"ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO" '
That line is actually what is being executed based on the output I see in my util, but what gets printed to the screen is the aforementioned minus the single quotes:
myutil setOptions "ONE\APPLE" "ONE\PEAR" "TWO\RED GRAPE" "TWO\TOMATO"
I need what is being displayed to the screen to be what is actually executed, not the version with the single quotes as that provides one giant parameter to myutil which is worthless.
I have two solutions, neither of which I'm sure is the best way to handle this.
The first is to simply use eval:
#!/bin/sh
MYCOMMAND=myutil
if [ -f myinput.txt ]; then
ARGSLIST=`cat myinput.txt| sed -e 's/^/"/g' -e 's/$/"/g' | awk '{ printf "%s ", $0 }'`
eval $MYCOMMAND setOptions "${ARGSLIST}"
printf "%s\n" "$MYCOMMAND setOptions ${ARGSLIST}"
fi
The second is to use xargs:
#!/bin/sh
MYCOMMAND=myutil
if [ -f myinput.txt ]; then
ARGSLIST=`cat myinput.txt| sed -e 's/^/"/g' -e 's/$/"/g' | awk '{ printf "%s ", $0 }'`
printf "%s\n" "$ARGSLIST" | xargs $MYCOMMAND setOptions
printf "%s\n" "$MYCOMMAND setOptions ${ARGSLIST}"
fi
I'm having a hard time believing that xargs is required, and I have been repeatedly reading how using eval is probably also not a recommended choice.
I have seen some similar topics regarding this with advice to use arrays, but I could not apply their advice properly to my example. Additionally I need this solution to run under bourne sh and be as portable as possible as it will be running on most standard flavors of Linux/UNIX. I don't believe sh supports arrays in the type that other solutions have recommended.
What is the best method for me to execute my command as it actually displays to the screen without the extra quoting being supplied by the shell?

Answer 1

You could define a recursive shell function which reads one line from its standard input at a time to build up the command line. When no more input is available, the actual command is run with the accumulated arguments. The recursion adds some overhead, but I'm assuming the input file isn't very big.
run_from_file () {
if IFS= read -r newarg; then
run_from_file "$#" "$newarg"
else
"$MYCOMMAND" "$#"
fi
}
run_from_file < myinput.txt