Most shell getopts have been annoying me for a long time, including lack of support of optional arguments.
But if you are willing to use "--posix" style arguments, visit bash argument case for args in $@
Question
I'd like to be able to accept both mandatory and optional flags in my script. Here's what I have so far.
#!bin/bash
while getopts ":a:b:cdef" opt; do
case $opt in
a ) APPLE="$OPTARG";;
b ) BANANA="$OPTARG";;
c ) CHERRY="$OPTARG";;
d ) DFRUIT="$OPTARG";;
e ) EGGPLANT="$OPTARG";;
f ) FIG="$OPTARG";;
\?) echo "Invalid option: -"$OPTARG"" >&2
exit 1;;
: ) echo "Option -"$OPTARG" requires an argument." >&2
exit 1;;
esac
done
echo "Apple is "$APPLE""
echo "Banana is "$BANANA""
echo "Cherry is "$CHERRY""
echo "Dfruit is "$DFRUIT""
echo "Eggplant is "$EGGPLANT""
echo "Fig is "$FIG""
However, the output for the following:
bash script.sh -a apple -b banana -c cherry -d dfruit -e eggplant -f fig
...outputs this:
Apple is apple
Banana is banana
Cherry is
Dfruit is
Eggplant is
Fig is
As you can see, the optional flags are not pulling the arguments with $OPTARG as it does with the required flags. Is there a way to read $OPTARG on optional flags without getting rid of the neat ":)" error handling?
EDIT: I wound up following the advice of Gilbert below. Here's what I did:
#!/bin/bash
if [[ "$1" =~ ^((-{1,2})([Hh]$|[Hh][Ee][Ll][Pp])|)$ ]]; then
print_usage; exit 1
else
while [[ $# -gt 0 ]]; do
opt="$1"
shift;
current_arg="$1"
if [[ "$current_arg" =~ ^-{1,2}.* ]]; then
echo "WARNING: You may have left an argument blank. Double check your command."
fi
case "$opt" in
"-a"|"--apple" ) APPLE="$1"; shift;;
"-b"|"--banana" ) BANANA="$1"; shift;;
"-c"|"--cherry" ) CHERRY="$1"; shift;;
"-d"|"--dfruit" ) DFRUIT="$1"; shift;;
"-e"|"--eggplant" ) EGGPLANT="$1"; shift;;
"-f"|"--fig" ) FIG="$1"; shift;;
* ) echo "ERROR: Invalid option: \""$opt"\"" >&2
exit 1;;
esac
done
fi
if [[ "$APPLE" == "" || "$BANANA" == "" ]]; then
echo "ERROR: Options -a and -b require arguments." >&2
exit 1
fi
Thanks so much, everyone. This works perfectly so far.
La solution 4
Most shell getopts have been annoying me for a long time, including lack of support of optional arguments.
But if you are willing to use "--posix" style arguments, visit bash argument case for args in $@
Autres conseils
:
means "takes an argument", not "mandatory argument". That is, an option character not followed by :
means a flag-style option (no argument), whereas an option character followed by :
means an option with an argument.
Thus, you probably want
getopts "a:b:c:d:e:f:" opt
If you want "mandatory" options (a bit of an oxymoron), you can check after argument parsing that your mandatory option values were all set.
It isn't easy... Any "optional" option arguments must actually be required as far as getopts
will know. Of course, an optional argument must be a part of the same argument to the script as the option it goes with. Otherwise an option -f
with an optional argument and an option -a
with a required argument can get confused:
# Is -a an option or an argument?
./script.sh -f -a foo
# -a is definitely an argument
./script.sh -f-a foo
The only way to do this is to test whether the option and its argument are in the same argument to the script. If so, OPTARG is the argument to the option. Otherwise, OPTIND must be decremented by one. Of course, the option is now required to have an argument, meaning a character will be found when an option is missing an argument. Just use another case
to determine if any options are required:
while getopts ":a:b:c:d:e:f:" opt; do
case $opt in
a) APPLE="$OPTARG";;
b) BANANA="$OPTARG";;
c|d|e|f)
if test "$OPTARG" = "$(eval echo '$'$((OPTIND - 1)))"; then
OPTIND=$((OPTIND - 1))
else
case $opt in
c) CHERRY="$OPTARG";;
d) DFRUIT="$OPTARG";;
...
esac
fi ;;
\?) ... ;;
:)
case "$OPTARG" in
c|d|e|f) ;; # Ignore missing arguments
*) echo "option requires an argument -- $OPTARG" >&2 ;;
esac ;;
esac
done
This has worked for me so far.
For bash, this is my favorite way to parse/support cli args. I used getopts and it was too frustrating that it wouldn't support long options. I do like how it works otherwise - especially for built-in functionality.
usage()
{
echo "usage: $0 -OPT1 <opt1_arg> -OPT2"
}
while [ "`echo $1 | cut -c1`" = "-" ]
do
case "$1" in
-OPT1)
OPT1_ARGV=$2
OPT1_BOOL=1
shift 2
;;
-OPT2)
OPT2_BOOL=1
shift 1
;;
*)
usage
exit 1
;;
esac
done
Short, simple. An engineer's best friend!
I think this can be modified to support "--" options as well...
Cheers =)
bash
's getopts
The bash
manual page (quoting the version 4.1 manual) for getopts
says:
getopts optstring name
[args]
getopts
is used by shell scripts to parse positional parameters. optstring contains the option characters to be recognized; if a character is followed by a colon, the option is expected to have an argument, which should be separated from it by white space. The colon (‘:’) and question mark (‘?’) may not be used as option characters. Each time it is invoked,getopts
places the next option in the shell variable name, initializing name if it does not exist, and the index of the next argument to be processed into the variableOPTIND
.OPTIND
is initialized to 1 each time the shell or a shell script is invoked. When an option requires an argument,getopts
places that argument into the variableOPTARG
. The shell does not resetOPTIND
automatically; it must be manually reset between multiple calls togetopts
within the same shell invocation if a new set of parameters is to be used.When the end of options is encountered,
getopts
exits with a return value greater than zero.OPTIND
is set to the index of the first non-option argument, and name is set to ‘?’.
getopts
normally parses the positional parameters, but if more arguments are given in args,getopts
parses those instead.
getopts
can report errors in two ways. If the first character of optstring is a colon, silent error reporting is used. In normal operation diagnostic messages are printed when invalid options or missing option arguments are encountered. If the variableOPTERR
is set to 0, no error messages will be displayed, even if the first character of optstring is not a colon.If an invalid option is seen,
getopts
places ‘?’ into name and, if not silent, prints an error message and unsetsOPTARG
. Ifgetopts
is silent, the option character found is placed inOPTARG
and no diagnostic message is printed. If a required argument is not found, andgetopts
is not silent, a question mark (‘?’) is placed in name,OPTARG
is unset, and a diagnostic message is printed. Ifgetopts
is silent, then a colon (‘:’) is placed in name andOPTARG
is set to the option character found.
Note that:
The leading colon in the option string puts getopts
into silent mode; it does not generate any error messages.
The description doesn't mention anything about optional option arguments.
I'm assuming that you are after functionality akin to:
script -ffilename
script -f
where the flag f
(-f
) optionally accepts an argument. This is not supported by bash
's getopts
command. The POSIX function getopt()
barely supports that notation. In effect, only the last option on a command line can have an optional argument under POSIX.
In part, consult Using getopts
in bash
shell script to get long and short command-line options.
The GNU getopt
(singular!) program is a complex beastie that supports long and short options and supports optional arguments for long options (and uses GNU getopt(3)
. Tracking its source is entertaining; the link on the page at die.net is wrong; you'll find it in a sub-directory under ftp://ftp.kernel.org/pub/linux/utils/util-linux (without the -ng
). I've not tracked down a location at http://www.gnu.org/ or http://www.fsf.org/ that contains it.
#!/bin/bash
while getopts ":a:b:c:d:e:f:" opt; do
case $opt in
a ) APPLE="$OPTARG";;
b ) BANANA="$OPTARG";;
c ) CHERRY="$OPTARG";;
d ) DFRUIT="$OPTARG";;
e ) EGGPLANT="$OPTARG";;
f ) FIG="$OPTARG";;
\?) echo "Invalid option: -"$OPTARG"" >&2
exit 1;;
: ) echo "Option -"$OPTARG" requires an argument." >&2
exit 1;;
esac
done
echo "Apple is "$APPLE""
echo "Banana is "$BANANA""
echo "Cherry is "$CHERRY""
echo "Dfruit is "$DFRUIT""
echo "Eggplant is "$EGGPLANT""
echo "Fig is "$FIG""