In python:
s = '1::3'
a = s.split(':')
print(a[0]) # '1' good
print(a[1]) # '' good
print(a[2]) # '3' good
How can I achieve the same effect with zsh?
The following attempt fails:
string="1::3"
a=(${(s/:/)string})
echo $a[1] # 1
echo $a[2] # 3 ?? I want an empty string, as in Python
The solution is to use the @ modifier, as indicated in the zsh docs:
string="1::3"
a=("${(@s/:/)string}") # @ modifier
By the way, if one has the choice of the delimiter, it's much easier and less error prone to use a newline as a delimiter. The right way to split the lines with zsh is then:
a=("${(f)string}")
I don't know whether or not the quotes are necessary here as well...
/s can be replaced with |s, it seems (e.g. a=(${(s|/|)string}")). I can't seem to find any documentation on this, though, so maybe there's some subtle behaviour change.
This will work in both zsh (with setopt shwordsplit or zsh -y) and Bash (zero-based arrays):
s="1::3"
saveIFS="$IFS"
IFS=':'
a=(${s})
IFS="$saveIFS"
echo ${a[1]} and echo ${a[3]} and get 1 and 3, respectively (the subscripts should be 0 and 2 for Bash). If it's short, post here what you tried and how exactly it failed. If it's a little longer, post a new question and link to it here.
IFS=':' cmd args..., so the change is coupled with the context/lifespan where it's expected/used. Then it's Not Your Job to know the prior values you aren't using, or to manage or recreate the outside environment, etc. - instead they clean themselves up.1, 1::3, ':'. The 1 is the first element of the array a which is the result of splitting s. See my earlier comments regarding better ways to output arrays. Something I didn't mention earlier is using local IFS=':' inside a function to limit the scope (but that doesn't apply to your original point).