Bash – Loop over a string in zsh and Bash

bashquotingvariablezsh

I would like to convert this Bash loop:

x="one two three"

for i in ${x}
do
    echo ${i}
done

in such a way to work with both Bash and zsh

This solution works:

x=( one two three )

for i in ${x[@]}
do
    echo ${i}
done

Anyway I am modifying x from a string to an array.

Is there a way to loop over $x in zsh when it is a string and in a way compatible with Bash?

I know about zsh setopt shwordsplit to emulate Bash, but I can't set it ad hoc for the loop, because it would not work in Bash.

Best Answer

if type emulate >/dev/null 2>/dev/null; then emulate ksh; fi

In zsh, this activates options that make it more compatible with ksh and bash, including sh_word_split. In other shells, emulate doesn't exist so this does nothing.

Related Solutions

Arrays and loops in zsh

Section 15.2.1 “Array Subscripts” says that arrays can be index with [exp] (where exp is a numeric expression) and that elements start at index 1 (0 if KSH_ARRAYS is set).

Section 14.3 “Parameter Expansion” says that the syntax ${#array_name} will expand to the number of elements of an array.

Section 6.3 “Complex Commands” gives the syntax for a numeric for loop (as in C):
for (( initExpr ; testExpr ; stepExpr )) do … done.

Putting them all together:

for (( i = 1; i <= $#LOCAL_PATH; i++ )) do
    ( # subshell to contain the effect of the chdir
        cd $LOCAL_PATH[i]
        hg pull $REMOTE_PATH[i]
    )
done

Or, if you are using KSH_ARRAYS, then this:

for (( i = 0; i < ${#LOCAL_PATH[@]}; i++ )) do
    ( # subshell to contain the effect of the chdir
        cd ${LOCAL_PATH[i]}
        hg pull ${REMOTE_PATH[i]}
    )
done

Using KSH_ARRAYS makes arrays start with index 0, requires the use of braces for array expressions, and interprets $array as $array[0] (requiring a change to the array length expression). The syntax changes required by KSH_ARRAY will also work without KSH_ARRAY, but you still have to adjust the logic for the different index range (1 through N versus 0 through N-1).

Bash string to int

Let awk do it:

df -P | awk 'NR == 2 { print $5+0; exit }'

Best Answer

Related Solutions

Arrays and loops in zsh

Bash string to int

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