support: properly check for bash as a dependency

PATCH New Yann E. MORIN 4 participants 8 messages Mar 17, 2014 – Mar 20, 2014

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Yann E. MORIN

author

2014-03-17 10:42 UTC #0 lore raw

PATCH 1/1 support: properly check for bash as a dependency

From: "Yann E. MORIN" <[email protected]>

The way we are checking for bash is to look if "$SHELL --version" will return a string containing "^GNU bash".

In case the system shell is dash (eg. /bin/sh -> /bin/dash), but the user's login shell is bash, dash will not override the SHELL variable:

    $ echo $SHELL
    /bin/bash
    $ /bin/dash
    $$ echo $SHELL
    /bin/bash

The same happens when called as the interpreter for a shell script:

    $ cat foo.sh
    #!/bin/dash
    echo $SHELL

    $ echo $SHELL
    /bin/bash
    $ ./foo.sh
    /bin/bash

So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.

Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.

Reported-by Andrew Barnes <[email protected]> (on IRC)

Signed-off-by "Yann E. MORIN" <[email protected]>

Cc Andrew Barnes <[email protected]>

---
 support/dependencies/dependencies.sh | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

support/dependencies/dependencies.sh +9 -4

index a8261b3..1b1a825 100755
@@ -138,11 +138,16 @@ if [ ! -z "$CXXCOMPILER" ] ; then
 	fi
 fi
 
-# Check bash
-if ! $SHELL --version 2>&1 | grep -q '^GNU bash'; then
+# Check bash is the system shell
+if ! /bin/sh --version 2>&1 | grep -q '^GNU bash'; then
 	echo
-	echo "You must install 'bash' on your build machine";
-	exit 1;
+	echo "You must install 'bash' on your build machine"
+	echo "and make it your default shell. On Debian-like"
+	echo "systems, this can be done with:"
+	echo "    sudo dpkg-reconfigure dash"
+	echo "and answer 'No' to the question:"
+	echo "    Use dash as the default system shell (/bin/sh)?"
+	exit 1
 fi;
 
 # Check that a few mandatory programs are installed

Signature · 1 line

1.8.3.2

Peter Korsgaard

2014-03-17 21:28 UTC #1 lore raw

PATCH 1/1 support: properly check for bash as a dependency

Quoted 27 lines

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"Yann" == Yann E MORIN <[email protected]> writes:
From: "Yann E. MORIN" <[email protected]>
The way we are checking for bash is to look if "$SHELL --version" will return a string containing "^GNU bash".
In case the system shell is dash (eg. /bin/sh -> /bin/dash), but the user's login shell is bash, dash will not override the SHELL variable:
    $ echo $SHELL
    /bin/bash
    $ /bin/dash
    $$ echo $SHELL
    /bin/bash
The same happens when called as the interpreter for a shell script:
    $ cat foo.sh
    #!/bin/dash
    echo $SHELL
    $ echo $SHELL
    /bin/bash
    $ ./foo.sh
    /bin/bash

Quoted 5 lines

So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.
Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.

Is that really still an issue? I just checked a few of the machines I often do buildroot builds on and they all have /bin/sh == dash.

support/dependencies/dependencies.sh if [ ! -z "$CXXCOMPILER" ] ; then · line 142

Quoted 4 lines

support/dependencies/dependencies.sh +2 -2

-# Check bash
-if ! $SHELL --version 2>&1 | grep -q '^GNU bash'; then
+# Check bash is the system shell
+if ! /bin/sh --version 2>&1 | grep -q '^GNU bash'; then

FYI, dash doesn't even understand a --version argument:

sh --version
sh: 0: Illegal option --

Signature · 1 line

Bye, Peter Korsgaard

Yann E. MORIN

author

2014-03-17 21:36 UTC #2 lore raw

PATCH 1/1 support: properly check for bash as a dependency

Peter, All,

On 2014-03-17 22:28 +0100, Peter Korsgaard spake thusly:

Quoted 27 lines

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"Yann" == Yann E MORIN <[email protected]> writes:
From: "Yann E. MORIN" <[email protected]>
The way we are checking for bash is to look if "$SHELL --version" will return a string containing "^GNU bash".
In case the system shell is dash (eg. /bin/sh -> /bin/dash), but the user's login shell is bash, dash will not override the SHELL variable:
    $ echo $SHELL
    /bin/bash
    $ /bin/dash
    $$ echo $SHELL
    /bin/bash
The same happens when called as the interpreter for a shell script:
    $ cat foo.sh
    #!/bin/dash
    echo $SHELL
    $ echo $SHELL
    /bin/bash
    $ ./foo.sh
    /bin/bash

Quoted 8 lines

Quoted 5 lines
So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.
Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.
Is that really still an issue? I just checked a few of the machines I often do buildroot builds on and they all have /bin/sh == dash.

Some configure-y scripts will run with /bin/sh, but have bashisms in them.

It was reported on IRC by Andrew that switching the system shell from dash to bash fixed an issue (Andrew, was that with libxml2?).

Quoted 6 lines

support/dependencies/dependencies.sh if [ ! -z "$CXXCOMPILER" ] ; then · line 142
Quoted 4 lines
support/dependencies/dependencies.sh +2 -2
-# Check bash
-if ! $SHELL --version 2>&1 | grep -q '^GNU bash'; then
+# Check bash is the system shell
+if ! /bin/sh --version 2>&1 | grep -q '^GNU bash'; then
FYI, dash doesn't even understand a --version argument:

Yes, but it surely does not return something matching "^GNU bash" which is all we care about.

Regards,
Yann E. MORIN.

Signature · 6 lines

.-----------------.--------------------.------------------.--------------------.
|  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  |
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'------------------------------^-------^------------------^--------------------'

Peter Korsgaard

2014-03-17 22:01 UTC #3 lore raw

PATCH 1/1 support: properly check for bash as a dependency

Quoted 11 lines

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"Yann" == Yann E MORIN <[email protected]> writes:
Peter, All,
Quoted 2 lines
Is that really still an issue? I just checked a few of the machines I often do buildroot builds on and they all have /bin/sh == dash.
Some configure-y scripts will run with /bin/sh, but have bashisms in them.
It was reported on IRC by Andrew that switching the system shell from dash to bash fixed an issue (Andrew, was that with libxml2?).

I don't think it is libxml2 as the stuff I'm currently doing at $WORK uses libxml2 and I haven't seen any issues with /bin/sh = dash.

Quoted 9 lines

Quoted 6 lines
support/dependencies/dependencies.sh if [ ! -z "$CXXCOMPILER" ] ; then · line 142
Quoted 4 lines
support/dependencies/dependencies.sh +2 -2
-# Check bash
-if ! $SHELL --version 2>&1 | grep -q '^GNU bash'; then
+# Check bash is the system shell
+if ! /bin/sh --version 2>&1 | grep -q '^GNU bash'; then
FYI, dash doesn't even understand a --version argument:
Yes, but it surely does not return something matching "^GNU bash" which is all we care about.

True.

Signature · 1 line

Bye, Peter Korsgaard

Thomas Petazzoni

2014-03-18 05:01 UTC #4 lore raw

PATCH 1/1 support: properly check for bash as a dependency

In reply to Yann E. MORIN

Dear Yann E. MORIN,

Quoted 5 lines · Yann E. MORIN

So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.
Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.

I'm definitely against that. My system has /bin/sh pointing to dash, and Buildroot works fine. One of the thing that annoyed me in OpenEmbedded was its requirements to have /bin/sh be bash.

We clearly don't want that.

I've just checked the Free Electrons autobuilders, and there are also using dash as /bin/sh. This means that if configure scripts were using bashims unsupported by dash, we would have noticed.

Thomas

Signature · 3 lines

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Yann E. MORIN

author

2014-03-18 16:55 UTC #5 lore raw

PATCH 1/1 support: properly check for bash as a dependency

Thomas, All,

On 2014-03-18 06:01 +0100, Thomas Petazzoni spake thusly:

Quoted 5 lines · Yann E. MORIN

Quoted 4 lines
So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.

Quoted 8 lines

Quoted 2 lines
Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.
I'm definitely against that. My system has /bin/sh pointing to dash, and Buildroot works fine. One of the thing that annoyed me in OpenEmbedded was its requirements to have /bin/sh be bash.
We clearly don't want that.

I'm just fine with that. :-)

But the current check is broken anyway, as all it checks is that the login shell of the user is bash.

- if we want to work whith dash as the system shell, then the current

    check is unneeded;

- if we want to work with dash as the system shell, we don't care what

    login shell the user is using, as we must also work when this is dash;

- SHELL is not mandated by POSIX, so it may be empty on a POSIX-compliant shell anyway.

So, we should just remove this check altogether.

Quoted 3 lines

I've just checked the Free Electrons autobuilders, and there are also using dash as /bin/sh. This means that if configure scripts were using bashims unsupported by dash, we would have noticed.

Andrew, what package was the breakage due to?

Regards,
Yann E. MORIN.

Signature · 6 lines

.-----------------.--------------------.------------------.--------------------.
|  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.  |
'------------------------------^-------^------------------^--------------------'

Thomas Petazzoni

2014-03-18 18:27 UTC #6 lore raw

PATCH 1/1 support: properly check for bash as a dependency

Dear Yann E. MORIN,

Quoted 14 lines · Yann E. MORIN

Quoted 5 lines
I'm definitely against that. My system has /bin/sh pointing to dash, and Buildroot works fine. One of the thing that annoyed me in OpenEmbedded was its requirements to have /bin/sh be bash.
We clearly don't want that.
I'm just fine with that. :-)
But the current check is broken anyway, as all it checks is that the login shell of the user is bash.
- if we want to work whith dash as the system shell, then the current
    check is unneeded;

Quoted 7 lines

- if we want to work with dash as the system shell, we don't care what
    login shell the user is using, as we must also work when this is dash;
- SHELL is not mandated by POSIX, so it may be empty on a POSIX-compliant shell anyway.
So, we should just remove this check altogether.

Yes, I agree.

Thomas

Signature · 3 lines

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Arnout Vandecappelle

2014-03-20 20:43 UTC #7 lore raw

PATCH 1/1 support: properly check for bash as a dependency

In reply to Yann E. MORIN

Quoted 7 lines · Yann E. MORIN

Thomas, All,
On 2014-03-18 06:01 +0100, Thomas Petazzoni spake thusly:
Quoted 4 lines · Yann E. MORIN
Quoted 3 lines
So, calling "$SHELL --version" will still return "^GNU bash" no matter what shell is actually running.

Have you tested this? dependencies.sh is run from the Makefile, and that
says:

SHELL:=$(shell if [ -x "$$BASH" ]; then echo $$BASH; \
else if [ -x /bin/bash ]; then echo /bin/bash; \
else echo sh; fi; fi)
[snip]

export SHELL CONFIG_SHELL quiet Q KBUILD_VERBOSE VERBOSE

So $SHELL _will_ be set to bash unless there is no bash.

Quoted 18 lines

Quoted 9 lines
Quoted 3 lines
Since quite a lot of #!/bin/sh scripts are in fact bash scripts, we really want to ensure that /bin/sh is bash.
I'm definitely against that. My system has /bin/sh pointing to dash, and Buildroot works fine. One of the thing that annoyed me in OpenEmbedded was its requirements to have /bin/sh be bash.
We clearly don't want that.
I'm just fine with that. :-)
But the current check is broken anyway, as all it checks is that the login shell of the user is bash.
- if we want to work whith dash as the system shell, then the current
    check is unneeded;

Quoted 7 lines

- if we want to work with dash as the system shell, we don't care what
    login shell the user is using, as we must also work when this is dash;
- SHELL is not mandated by POSIX, so it may be empty on a POSIX-compliant shell anyway.
So, we should just remove this check altogether.

Not remove, but rather replace it with a check for /bin/bash existence.
We do have quite a lot of stuff referring to /bin/bash. bash in PATH is not good enough.

Regards,
Arnout

Quoted 10 lines

Quoted 4 lines
I've just checked the Free Electrons autobuilders, and there are also using dash as /bin/sh. This means that if configure scripts were using bashims unsupported by dash, we would have noticed.
Andrew, what package was the breakage due to?
Regards,
Yann E. MORIN.

Signature · 6 lines

Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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