Re: [PATCH v2 001/142] check-builtins.sh: use the $( ... ) construct for command substitution

Junio C Hamano [off-list ref] writes:

Elia Pinto [off-list ref] writes:

quoted

The Git CodingGuidelines prefer the $( ... ) construct for command
substitution instead of using the back-quotes, or grave accents (`..`).

The backquoted form is the historical method for command substitution,
and is supported by POSIX. However, all but the simplest uses become
complicated quickly. In particular, embedded command substitutions
and/or the use of double quotes require careful escaping with the backslash
character. Because of this the POSIX shell adopted the $(…) feature from
the Korn shell.

The patch was generated by the simple script

for _f in $(find . -name "*.sh")
do
  sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
done

"and then carefully proofread" is sorely needed here.

What is that non-breaking space doing at the beginning of an
indented line, or is it just my environment, by the way?

I've reworded the above like so:

    check-builtins.sh: use the $(...) construct for command substitution
    
    The Git CodingGuidelines prefer the $(...) construct for command
    substitution instead of using the backquotes, or grave accents
    (`...`).
    
    The backquoted form is the historical method for command
    substitution, and is supported by POSIX.  However, all but the
    simplest uses become complicated quickly.  In particular, embedded
    command substitutions and/or the use of double quotes require
    careful escaping with the backslash character.
    
    The patch was generated by:
    
        for _f in $(find . -name "*.sh")
        do
          sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
        done
    
    and then carefully proof-read.
    
    Signed-off-by: Elia Pinto [off-list ref]
    Signed-off-by: Junio C Hamano [off-list ref]


I looked at [*1*] to pick between "back-quote" and "backquote"; this
is a related tangent, but in that page, you will find this gem:

    Within the backquoted style of command substitution, <backslash>
    shall retain its literal meaning, except when followed by: '$',
    '`', or <backslash>.

Stated another way, `` => $() conversion will make backslash inside
to bahave differently, and we would need to be careful when doing
such a change.

I've looked at and queued 001 and 002.


[Reference]

*1* http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_03