threads / patch / 41328

patch, 15 partsgit-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

Subject: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

## tl;dr

9 messages between Feb 4, 2016 and Feb 5, 2016. Diffs are folded; open one to read it.

replies: 8people: 5as markdown or json

Elia Pinto· Feb 4, 2016, 10:20 UTC · lore

expr is considered generally antiquated. It is best to use for arithmetic operations the shell $((..)).

To quote POSIX:

"The expr utility has a rather difficult syntax [...] In many cases, the arithmetic and string features provided as part of the shell command language are easier to use than their equivalents in expr. Newly written scripts should avoid expr in favor of the new features within the shell."

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
---
 git-am.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Show changes to git-am.sh +3 −3

diff --git a/git-am.sh b/git-am.sh
index ee61a77..4f8148e 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -298,7 +298,7 @@ split_patches () {
 		this=0
 		for stgit in "$@"
 		do
-			this=$(expr "$this" + 1)
+			this=$(( "$this" + 1 ))
 			msgnum=$(printf "%0${prec}d" $this)
 			# Perl version of StGIT parse_patch. The first nonemptyline
 			# not starting with Author, From or Date is the
@@ -656,14 +656,14 @@ last=$(cat "$dotest/last")
 this=$(cat "$dotest/next")
 if test "$skip" = t
 then
-	this=$(expr "$this" + 1)
+	this=$(( "$this" + 1 ))
 	resume=
 fi
 
 while test "$this" -le "$last"
 do
 	msgnum=$(printf "%0${prec}d" $this)
-	next=$(expr "$this" + 1)
+	next=$(( "$this" + 1 ))
 	test -f "$dotest/$msgnum" || {
 		resume=
 		go_next

-- 
2.5.0

Elia Pinto· Feb 4, 2016, 10:20 UTC · re: Elia Pinto · lore

[PATCH 15/15] t4032-diff-inter-hunk-context.sh: replace using expr for arithmetic operations with the equivalent shell builtin

expr is considered generally antiquated. It is best to use for arithmetic operations the shell $((..)).

To quote POSIX:

    "The expr utility has a rather difficult syntax [...] In many cases, the arithmetic
    and string features provided as part of the shell command language are easier to use
    than their equivalents in expr. Newly written scripts should avoid expr in favor of
    the new features within the shell."

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
---
 t/t4032-diff-inter-hunk-context.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Show changes to t/t4032-diff-inter-hunk-context.sh +1 −1

diff --git a/t/t4032-diff-inter-hunk-context.sh b/t/t4032-diff-inter-hunk-context.sh
index e4e3e28..0b0b60f 100755
--- a/t/t4032-diff-inter-hunk-context.sh
+++ b/t/t4032-diff-inter-hunk-context.sh
@@ -10,7 +10,7 @@ f() {
 	while test $i -le $2
 	do
 		echo $i
-		i=$(expr $i + 1)
+		i=$(( $i + 1 ))
 	done
 	echo $3
 }

-- 
2.5.0

Johannes Schindelin· Feb 4, 2016, 11:14 UTC · re: Elia Pinto · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

Hi Elia,

On Thu, 4 Feb 2016, Elia Pinto wrote:

> -			this=$(expr "$this" + 1)
> +			this=$(( "$this" + 1 ))

Why the funny spaces? We do not do that anywhere in the existing code except in three places (2x filter-branch, 1x rebase--interactive, all three *not* my fault) and in some tests.

Also, I am *pretty* certain that the quotes break this code:

	me@work MINGW64 /usr/src/git (master)
	$ this=1

	me@work MINGW64 /usr/src/git (master)
	$ this=$(( "$this" + 1 ))
	bash: "1" + 1 : syntax error: operand expected (error token is ""1" + 1 ")

Whereas if you do *not* add the superfluous spaces and quotes, it works:

	me@work MINGW64 /usr/src/git (master)
	$ this=1

	me@work MINGW64 /usr/src/git (master)
	$ this=$(($this+1))

	me@work MINGW64 /usr/src/git (master)
	$ echo $this
	2

Maybe this is only a problem with Bash 4.3.42 in MSYS2, but I do not think so.

*Clicketyclick*

Nope. It also happens in Ubuntu's Bash 4.3.42:

	me@ubuntu-vm  ~/git (master)
	$ this=1

	me@ubuntu-vm  ~/git (master)
	$ this=$(( "$this" + 1 ))
	bash: "1" + 1 : syntax error: operand expected (error token is ""1" + 1 ")

	me@ubuntu-vm  ~/git (master)
	$ bash --version
	GNU bash, version 4.3.42(1)-release (x86_64-pc-linux-gnu)
	Copyright (C) 2013 Free Software Foundation, Inc.
	License GPLv3+: GNU GPL version 3 or later
	<http://gnu.org/licenses/gpl.html>

	This is free software; you are free to change and redistribute it.
	There is NO WARRANTY, to the extent permitted by law.

... which makes me wonder in which environment you tested this?

Ciao, Dscho

Elia Pinto· Feb 4, 2016, 11:53 UTC · re: Johannes Schindelin · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

2016-02-04 12:14 GMT+01:00 Johannes Schindelin <Johannes.Schindelin@gmx.de>:

Show 26 quoted lines

> Hi Elia,
>
> On Thu, 4 Feb 2016, Elia Pinto wrote:
>
>> -                     this=$(expr "$this" + 1)
>> +                     this=$(( "$this" + 1 ))
>
> Why the funny spaces? We do not do that anywhere in the existing code
> except in three places (2x filter-branch, 1x rebase--interactive, all
> three *not* my fault) and in some tests.
>
> Also, I am *pretty* certain that the quotes break this code:
>
>         me@work MINGW64 /usr/src/git (master)
>         $ this=1
>
>         me@work MINGW64 /usr/src/git (master)
>         $ this=$(( "$this" + 1 ))
>         bash: "1" + 1 : syntax error: operand expected (error token is ""1" + 1 ")
>
> Whereas if you do *not* add the superfluous spaces and quotes, it works:
>
>         me@work MINGW64 /usr/src/git (master)
>         $ this=1
>
>         me@work MINGW64 /usr/src/git (master)

Thanks for noticing.

You are right. I ran the test but did not notice mistakes, my fault.

I will resend. Thanks again.

Best

Show 34 quoted lines

>         $ this=$(($this+1))
>
>         me@work MINGW64 /usr/src/git (master)
>         $ echo $this
>         2
>
> Maybe this is only a problem with Bash 4.3.42 in MSYS2, but I do not think
> so.
>
> *Clicketyclick*
>
> Nope. It also happens in Ubuntu's Bash 4.3.42:
>
>         me@ubuntu-vm  ~/git (master)
>         $ this=1
>
>         me@ubuntu-vm  ~/git (master)
>         $ this=$(( "$this" + 1 ))
>         bash: "1" + 1 : syntax error: operand expected (error token is ""1" + 1 ")
>
>         me@ubuntu-vm  ~/git (master)
>         $ bash --version
>         GNU bash, version 4.3.42(1)-release (x86_64-pc-linux-gnu)
>         Copyright (C) 2013 Free Software Foundation, Inc.
>         License GPLv3+: GNU GPL version 3 or later
>         <http://gnu.org/licenses/gpl.html>
>
>         This is free software; you are free to change and redistribute it.
>         There is NO WARRANTY, to the extent permitted by law.
>
> ... which makes me wonder in which environment you tested this?
>
> Ciao,
> Dscho

Johannes Schindelin· Feb 4, 2016, 12:01 UTC · re: Elia Pinto · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

Hi Elia,

On Thu, 4 Feb 2016, Elia Pinto wrote:

Show 11 quoted lines

> 2016-02-04 12:14 GMT+01:00 Johannes Schindelin <Johannes.Schindelin@gmx.de>:
> > Hi Elia,
> >
> > On Thu, 4 Feb 2016, Elia Pinto wrote:
> >
> >> -                     this=$(expr "$this" + 1)
> >> +                     this=$(( "$this" + 1 ))
> >
> > Why the funny spaces? We do not do that anywhere in the existing code
> > except in three places (2x filter-branch, 1x rebase--interactive, all
> > three *not* my fault) and in some tests.

I actually noticed more places now, and will send a quick fixer-upper patch series in a few seconds, that we can hopefully apply before your series?

Thanks, Dscho

Junio C Hamano· Feb 4, 2016, 19:33 UTC · re: Elia Pinto · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

As pointed out already, quoting of "$this" inside the arithmetic expansion would not work very well, so [14/15] needs fixing.

I do not see 01/15 thru 13/15 here, by the way.  Is it just me?

Eric Sunshine· Feb 4, 2016, 19:39 UTC · re: Junio C Hamano · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

On Thu, Feb 4, 2016 at 2:33 PM, Junio C Hamano <gitster@pobox.com> wrote:

> As pointed out already, quoting of "$this" inside the arithmetic
> expansion would not work very well, so [14/15] needs fixing.
>
> I do not see 01/15 thru 13/15 here, by the way.  Is it just me?

I didn't receive them either, and they don't seem to be on gmane...

Elia Pinto· Feb 5, 2016, 12:50 UTC · re: Junio C Hamano · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

2016-02-04 20:33 GMT+01:00 Junio C Hamano <gitster@pobox.com>:

> As pointed out already, quoting of "$this" inside the arithmetic
> expansion would not work very well, so [14/15] needs fixing.
>
> I do not see 01/15 thru 13/15 here, by the way.  Is it just me?

Excuse me, everyone. Yesterday was a bad day. I did a bit of confusion :=(. But this is not a patch series, yes. The patch is for git-am in contrib: so it is not important.

Thank you

Stefan Beller· Feb 4, 2016, 19:46 UTC · re: Elia Pinto · lore

Re: [PATCH 14/15] git-am.sh: replace using expr for arithmetic operations with the equivalent shell builtin

On which version did you base your patches?

git-am.sh is no more since 2015-08-04, (it was moved to contrib/examples/git-am.sh as part of the rewrite of am in C)