[PATCH] scripts/config: use sed's POSIX interface

[PATCH] scripts/config: use sed's POSIX interface

[Clement Chauplannaz]

Script `config' relies on extensions of `GNU sed', and is thus not
working on all Unixes:
- in-place edition of files (-i), which can be replaced with
a temporary file;
- extended-regexps (-r), which can be split into basic regexps;
- single-line calls to `a' command, while some implementations
require a leading newline before the parameter.

Rewrite calls to `sed' program to comply with POSIX interface.

Signed-off-by: Clement Chauplannaz <chauplac@gmail.com>
---
 scripts/config | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/scripts/config b/scripts/config
index a65ecbb..3fd95eb 100755
--- a/scripts/config
+++ b/scripts/config
@@ -66,9 +66,14 @@ set_var() {
 	name_re="^($name=|# $name is not set)"
 	before_re="^($before=|# $before is not set)"
 	if test -n "$before" && grep -Eq "$before_re" "$FN"; then
-		sed -ri "/$before_re/a $new" "$FN"
+		lf=$'\n'
+		sed -e "/^$before=/a\\$lf$new$lf" \
+		    -e "/^# $before is not set/a\\$lf$new$lf" "$FN" >"$FN.swp"
+		mv "$FN.swp" "$FN"
 	elif grep -Eq "$name_re" "$FN"; then
-		sed -ri "s:$name_re.*:$new:" "$FN"
+		sed -e "s:^$name=.*:$new:" \
+		    -e "s:^# $name is not set:$new:" "$FN" >"$FN.swp"
+		mv "$FN.swp" "$FN"
 	else
 		echo "$new" >>"$FN"
 	fi
@@ -77,7 +82,8 @@ set_var() {
 undef_var() {
 	local name=$1
 
-	sed -ri "/^($name=|# $name is not set)/d" "$FN"
+	sed -e "/^$name=/d" -e "/^# $name is not set/d" "$FN" >"$FN.swp"
+	mv "$FN.swp" "$FN"
 }
 
 if [ "$1" = "--file" ]; then
-- 
1.8.3.rc1.44.gb387c77.dirty

Re: [PATCH] scripts/config: use sed's POSIX interface

[Yann E. MORIN]

Clément, All,

On 2013-07-10 21:58 +0200, Clement Chauplannaz spake thusly:
> Script `config' relies on extensions of `GNU sed', and is thus not
> working on all Unixes:
> - in-place edition of files (-i), which can be replaced with
> a temporary file;
> - extended-regexps (-r), which can be split into basic regexps;
> - single-line calls to `a' command, while some implementations
> require a leading newline before the parameter.
> 
> Rewrite calls to `sed' program to comply with POSIX interface.

Clément, sorry I did not come back to you earlier after your second PM.
Here is further review:

> Signed-off-by: Clement Chauplannaz <chauplac@gmail.com>
> ---
>  scripts/config | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/config b/scripts/config
> index a65ecbb..3fd95eb 100755
> --- a/scripts/config
> +++ b/scripts/config
> @@ -66,9 +66,14 @@ set_var() {
>  	name_re="^($name=|# $name is not set)"
>  	before_re="^($before=|# $before is not set)"
>  	if test -n "$before" && grep -Eq "$before_re" "$FN"; then
> -		sed -ri "/$before_re/a $new" "$FN"
> +		lf=$'\n'

As you explained me earlier, you expect this to actually set the '\n'
symbol (0x0a) as first char of variable 'lf'. This is a bashism, and is
not POSIX. Here is a test script:

    #!/bin/dash
    lf=$'\n'
    printf "lf='%s'\n" "${lf}"
    printf "lf='${lf}'\n"

And the output:
    lf='$\n'
    lf='$
    '

Now, if you use #!/bin/bash, it works as you expect, but not with a
POSIX-only script like dash.

A reliable way to get a single '\n' would be:

    lf="$( printf '\n' )"

Yes, config is already a bash script, but no need to add bashisms when
they can be avoided. And since this patch is about POSIX compliance in
the first place... ;-)

Otherwise, LGTM.

Regards,
Yann E. MORIN.

-- 
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| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
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'------------------------------^-------^------------------^--------------------'

Re: [PATCH] scripts/config: use sed's POSIX interface

[Clément Chauplannaz]

Yann

2013/7/10 Yann E. MORIN <yann.morin.1998@free.fr>:
> Clément, All,
>
> On 2013-07-10 21:58 +0200, Clement Chauplannaz spake thusly:
>> Script `config' relies on extensions of `GNU sed', and is thus not
>> working on all Unixes:
>> - in-place edition of files (-i), which can be replaced with
>> a temporary file;
>> - extended-regexps (-r), which can be split into basic regexps;
>> - single-line calls to `a' command, while some implementations
>> require a leading newline before the parameter.
>>
>> Rewrite calls to `sed' program to comply with POSIX interface.
>
> Clément, sorry I did not come back to you earlier after your second PM.
> Here is further review:
>
>> Signed-off-by: Clement Chauplannaz <chauplac@gmail.com>
>> ---
>>  scripts/config | 12 +++++++++---
>>  1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/scripts/config b/scripts/config
>> index a65ecbb..3fd95eb 100755
>> --- a/scripts/config
>> +++ b/scripts/config
>> @@ -66,9 +66,14 @@ set_var() {
>>       name_re="^($name=|# $name is not set)"
>>       before_re="^($before=|# $before is not set)"
>>       if test -n "$before" && grep -Eq "$before_re" "$FN"; then
>> -             sed -ri "/$before_re/a $new" "$FN"
>> +             lf=$'\n'
>
> As you explained me earlier, you expect this to actually set the '\n'
> symbol (0x0a) as first char of variable 'lf'. This is a bashism, and is
> not POSIX. Here is a test script:
>
>     #!/bin/dash
>     lf=$'\n'
>     printf "lf='%s'\n" "${lf}"
>     printf "lf='${lf}'\n"
>
> And the output:
>     lf='$\n'
>     lf='$
>     '
>
> Now, if you use #!/bin/bash, it works as you expect, but not with a
> POSIX-only script like dash.
>
> A reliable way to get a single '\n' would be:
>
>     lf="$( printf '\n' )"
This looks like a good idea. I need to work it more in depth though,
as the "single-newline" printf seems to get caught by bash as an IFS -
in other words, it produces an empty var. I'll come back to you with
my findings.

>
> Yes, config is already a bash script, but no need to add bashisms when
> they can be avoided. And since this patch is about POSIX compliance in
> the first place... ;-)
Well, it's more about POSIX compliance for utilities (grep, sed, find,
etc.) which share the same name, a somewhat loose common interface,
but a different implementation between GNU & *BSD. I'm assuming bash
under Linux and *BSD comes from the same source :-).
Besides, I can't say to what extent `config' script complies with
POSIX shell interface and how it would run under other shells...
>
> Otherwise, LGTM.
>
Best regards,
Clement

> Regards,
> Yann E. MORIN.
>
> --
> .-----------------.--------------------.------------------.--------------------.
> |  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
> | +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
> | +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
> | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
> '------------------------------^-------^------------------^--------------------'