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These are like the YSH vs. Shell Idioms, but the advice also applies to other Unix shells.
"$@"
There's no reason to use anything but "$@"
. All the other forms like $*
can be disallowed, because if you want to join to a string, you can write:
joined_str="$@"
The same advice applies to arrays. You can always use "${myarray[@]}"
; you
never need to use ${myarray[*]}
or any other form.
Related: Thirteen Incorrect Ways and Two Awkward Ways to Use Arrays
test
to [
Idiomatic OSH code doesn't use "puns".
No:
[ -d /tmp ]
Yes:
test -d /tmp
The simple_test_builtin option enforces this.
Static parsing is one of the syntactic concepts. It leads to better error messages, earlier error messages, and lets tools understand your code.
test
Should Only Have 2 or 3 ArgumentsIn POSIX, the test
builtin has a lot of unnecessary flexibility, which leads
to bugs.
See Problems With the test Builtin: What Does -a Mean?
No:
test ! -d /tmp
test -d /tmp -a -d /tmp/foo
Yes:
! test -d /tmp
test -d /tmp && test -d /tmp/foo
The simple_test_builtin option enforces that
test
receives 3 or fewer arguments.
Functions subsume all the common uses of alias, and can be parsed statically.
No:
alias ll='ls -l'
Yes:
ll() { # Shell Style
ls -l "$@"
}
proc ll { # YSH Style
ls -l @ARGV
}
If you're wrapping an external command with a function of the same, use the command builtin:
proc ls {
command ls --color @ARGV
}
$'\n'
to echo -e
No:
echo -e '\n' # arg to -e is dynamically parsed
Yes:
echo $'\n' # statically parsed
strict_errexit
DisallowsThe strict_errexit
feature warns you when you would lose errors in shell
code.
local d=$(date %x)
PitfallNo:
local d=$(date %x) # ignores failure
Yes:
local d
d=$(date %x) # fails properly
Better YSH style:
var d = $(date %x) # fails properly
readonly
and export
In these cases, the builtin comes after the assignment.
No:
readonly d1=$(date %x)
export d2=$(date %x)
Yes:
d1=$(date %x)
readonly d1
d2=$(date %x)
export d2
if myfunc
PitfallNo:
if myfunc; then
echo 'Success'
fi
Shell workaround when the $0 Dispatch Pattern is used:
myfunc() {
echo hi
}
mycaller() {
if $0 myfunc; then # $0 starts this script as a new process
echo 'Success'
fi
}
"$@" # invoked like myscript.sh mycaller arg1 arg2 ...
Better YSH Style:
try {
myfunc
}
if (_error.code === 0)
echo 'Success'
}
declare -i
, local -i
, ...The -i
flag on assignment builtins doesn't add any functionality to bash —
it's merely a different and confusing style.
OSH doesn't support it; instead it has true integers.
For example, don't rely on "punning" of the +=
operator; use $(( ))
instead.
No:
declare -i x=3
x+=1 # Now it's '4' because += will do integer arithmetic
Yes (shell style):
x=3
x=$(( x + 1 )) # No -i flag needed
Yes (YSH style):
var x = 3
setvar x += 1
Likewise, don't rely on dynamic parsing of arithmetic.
No:
declare -i x
x='1 + 2' # Now it's the string '3'
Yes (shell style):
x=$(( 1 + 2 ))
Yes (YSH style):
var x = 1 + 2