AIX Open Source

In the latest release of Bash on the toolbox website (5.0 Patch 18) I am running into a problem with one of my scripts and have isolated the issue.  I did downgrade to the previous version of Bash from the toolbox (5.0, no patches) and it works fine.

What is happening is when I run a command (such as 'ls -al /etc') with a while loop and read the line it works fine sometimes but sometimes it does not.  When it does not work fine it hangs once it reaches the end of the input that is being fed into the loop, it should see the EOF and automatically terminate but it does not.  This previously worked fine 100% of the time.



------------------------------
Mike Whitton
------------------------------

I downloaded the official GNU release, patched it to version 5.0.18, the same release IBM is distributing, and it is working fine.  The GCC compilers and GNU Make were used to build this package.

There is possibly something wrong with the version that is being distributed on the IBM AIX Linux Toolbox website.

Thanks

------------------------------
Mike Whitton
------------------------------

Original Message:
Sent: Mon April 19, 2021 05:11 PM
From: Mike Whitton
Subject: Issue with Bash read builtin in latest release


In the latest release of Bash on the toolbox website (5.0 Patch 18) I am running into a problem with one of my scripts and have isolated the issue.  I did downgrade to the previous version of Bash from the toolbox (5.0, no patches) and it works fine.

What is happening is when I run a command (such as 'ls -al /etc') with a while loop and read the line it works fine sometimes but sometimes it does not.  When it does not work fine it hangs once it reaches the end of the input that is being fed into the loop, it should see the EOF and automatically terminate but it does not.  This previously worked fine 100% of the time.

I trussed the output and this is what we are getting when we reach the end of the line:

     kfcntl(2, F_GETFL, 0x0FFFFFFFFFFFFFE8)          = 67110914
     kioctl(0, 22528, 0x0000000000000000, 0x0000000000000000) Err#25 ENOTTY
     lseek(0, 0, 1)                                  Err#29 ESPIPE
     kread(0, "\t", 1)               (sleeping...)

When it is working the kread function does not sleep, it just moves onto the next iteration in the while loop.

Here is a sample piece of code to recreate the issue:

      SGLIST=("testfile1" "testfile1" "testfile1" "testfile1") 

      for sg in ${SGLIST[@]}
      do
              while read line
              do
                      echo $line
              done < <(ls -al /etc 2>&1)
       done

This particular sample code reliably fails every time.  The piece of code I have written fails with the same basic setup one out of every four times or so.  

Any thoughts on this?

Thanks

------------------------------
Mike Whitton
------------------------------

Strange, running your script, it doesn't end, it stands on the last read:
<root@t0201:/home/00000217/testdir>./testhg2.sh
SGLIST=("testfile1" "testfile1" "testfile1" "testfile1")
+ SGLIST=("testfile1" "testfile1" "testfile1" "testfile1")

for sg in ${SGLIST[@]}
do
while read line
do
echo "$line"
done < <(ls -al ./ 2>&1)
done
+ for sg in ${SGLIST[@]}
+ read line
++ ls -al ./
+ echo 'total 32'
total 32
+ read line
+ echo 'drwxr-xr-x 2 root system 256 Apr 21 09:12 .'
drwxr-xr-x 2 root system 256 Apr 21 09:12 .
+ read line
+ echo 'drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..'
drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..
+ read line
+ echo '-rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh'
-rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh
+ read line
+ echo '-rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh'
-rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh
+ read line
+ echo '-rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh'
-rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh
+ read line

Now I modified it slightly and it works (run it 50 times):

<root@t0201:/home/00000217/testdir>cat testhga.sh
!/bin/bash
echo "bash version: ${BASH_VERSINFO}"
rpm -qa |grep bash


SGLIST=("testfile1" "testfile1" "testfile1" "testfile1")
i=0
for sg in ${SGLIST[@]}
do
let i=i+1
echo "Loop $i"
j=0
while read line
do
let j=j+1
echo "Loop $i MYLINE: $line"
done < <(ls -al ./ 2>&1)
done
<root@t0201:/home/00000217/testdir>kkk
<root@t0201:/home/00000217/testdir>./testhga.sh
./testhga.sh: line 1: !/bin/bash: No such file or directory
bash version: 5
bash-5.0.18-1.ppc
Loop 1
Loop 1 MYLINE: total 32
Loop 1 MYLINE: drwxr-xr-x 2 root system 256 Apr 21 09:12 .
Loop 1 MYLINE: drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..
Loop 1 MYLINE: -rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh
Loop 1 MYLINE: -rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh
Loop 1 MYLINE: -rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh
Loop 2
Loop 2 MYLINE: total 32
Loop 2 MYLINE: drwxr-xr-x 2 root system 256 Apr 21 09:12 .
Loop 2 MYLINE: drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..
Loop 2 MYLINE: -rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh
Loop 2 MYLINE: -rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh
Loop 2 MYLINE: -rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh
Loop 3
Loop 3 MYLINE: total 32
Loop 3 MYLINE: drwxr-xr-x 2 root system 256 Apr 21 09:12 .
Loop 3 MYLINE: drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..
Loop 3 MYLINE: -rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh
Loop 3 MYLINE: -rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh
Loop 3 MYLINE: -rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh
Loop 4
Loop 4 MYLINE: total 32
Loop 4 MYLINE: drwxr-xr-x 2 root system 256 Apr 21 09:12 .
Loop 4 MYLINE: drwxr-xr-x 7 00000217 staff 4096 Apr 21 09:04 ..
Loop 4 MYLINE: -rwxr-xr-x 1 root system 179 Apr 21 09:15 testhg2.sh
Loop 4 MYLINE: -rwxr-xr-x 1 root system 378 Apr 21 09:26 testhga.sh
Loop 4 MYLINE: -rwxr-xr-x 1 root system 381 Apr 21 09:12 testhgb.sh
<root@t0201:/home/00000217/testdir>

------------------------------
Achim Haag
------------------------------

Original Message:
Sent: Tue April 20, 2021 12:57 PM
From: Mike Whitton
Subject: Issue with Bash read builtin in latest release


I downloaded the official GNU release, patched it to version 5.0.18, the same release IBM is distributing, and it is working fine.  The GCC compilers and GNU Make were used to build this package.

There is possibly something wrong with the version that is being distributed on the IBM AIX Linux Toolbox website.

Thanks

------------------------------
Mike Whitton

Original Message:
Sent: Mon April 19, 2021 05:11 PM
From: Mike Whitton
Subject: Issue with Bash read builtin in latest release


In the latest release of Bash on the toolbox website (5.0 Patch 18) I am running into a problem with one of my scripts and have isolated the issue.  I did downgrade to the previous version of Bash from the toolbox (5.0, no patches) and it works fine.

What is happening is when I run a command (such as 'ls -al /etc') with a while loop and read the line it works fine sometimes but sometimes it does not.  When it does not work fine it hangs once it reaches the end of the input that is being fed into the loop, it should see the EOF and automatically terminate but it does not.  This previously worked fine 100% of the time.

I trussed the output and this is what we are getting when we reach the end of the line:

     kfcntl(2, F_GETFL, 0x0FFFFFFFFFFFFFE8)          = 67110914
     kioctl(0, 22528, 0x0000000000000000, 0x0000000000000000) Err#25 ENOTTY
     lseek(0, 0, 1)                                  Err#29 ESPIPE
     kread(0, "\t", 1)               (sleeping...)

When it is working the kread function does not sleep, it just moves onto the next iteration in the while loop.

Here is a sample piece of code to recreate the issue:

      SGLIST=("testfile1" "testfile1" "testfile1" "testfile1") 

      for sg in ${SGLIST[@]}
      do
              while read line
              do
                      echo $line
              done < <(ls -al /etc 2>&1)
       done

This particular sample code reliably fails every time.  The piece of code I have written fails with the same basic setup one out of every four times or so.  

Any thoughts on this?

Thanks

------------------------------
Mike Whitton
------------------------------