Updated ksh packages that fix several bugs are now available for Red Hat Enterprise Linux 6.
KornShell (ksh) is a Unix shell developed by AT&T Bell Laboratories, which is backward-compatible with the Bourne shell (Bash) and includes many features of the C shell. The most recent version is KSH-93. KornShell complies with the POSIX.2 standard (IEEE Std 1003.2-1992).
- Due to a race condition in the job list code, the ksh shell could terminate unexpectedly with a segmentation fault when the user had run custom scripts on their system. The race condition has been fixed, and ksh now works as expected when the users run custom scripts.
- Due to a regression bug, a command substitution containing a pipe could return a non-zero exit code even though the command did not fail. A patch has been provided to fix this bug, and these command substitutions now return correct exit codes.
- Previously, if a running function was unset by another function in a ksh script, ksh terminated unexpectedly with a segmentation fault. With this update, the ksh code skips resetting of the "running" flag if a function is unset, and ksh no longer crashes in the described scenario.
- Previously, using the typeset command in a function in ksh resulted in a memory leak. This bug has been fixed and ksh no longer leaks memory when using the typeset command in a function.
- Previously after upgrading ksh from version "ksh-20100621-19" to "ksh-20120801-10", the standard error output (stderr) got disconnected from the terminal, and the trace output in debug mode thus became invisible. As a consequence, the debugging of scripts on ksh was not always possible. This bug has been fixed and stderr now provides the correct output.
- Previously, a substitution command failed to execute in ksh if the standard input (stdin), the standard output (stdout), or standard error (stderr) were closed in a certain manner. As a consequence, reading a file using command substitution did not work correctly and the substituted text failed to display under some circumstances. A patch has been applied to address this bug, and command substitution now works as expected.
- Prior to this update, the compiler optimization dropped parts of the ksh job locking mechanism from the binary code. As a consequence, ksh could terminate unexpectedly with a segmentation fault after it received the SIGCHLD signal. This update ensures that the compiler does not drop parts of the ksh job locking mechanism and ksh works as expected.
- When running a command that output a lot of data, and then setting a variable from that output, the ksh could become unresponsive. To fix this problem, the combination of I/O redirection and synchronization mechanism has been changed. Now, ksh no longer hangs in this case and commands with large data output complete successfully.
- Previously, the ksh syntax analyzer did not parse command substitutions inside of here-documents correctly, which led to syntax error messages being reported on the syntactically correct code. A patch has been provided to fix this bug, and ksh now interprets substitutes as intended.
- Previously, ksh could skip setting of an exit code from the last command of a function. As a result, the function could sometimes return a wrong exit code. This update ensures that ksh always uses the exit code from the last command of a function, and functions in ksh now return the correct exit codes as expected.
- When rounding off a number smaller than 1, ksh incorrectly truncated too many decimals. As a consequence, numbers from the interval between 0.5 and 0.999 were incorrectly rounded to zero. This updated version of ksh ensures that all numbers are now rounded off correctly.
- Previously, ksh did not handle the brace expansion option correctly and ignored it in most cases. As a result, it was not possible to turn the brace expansion off and braces in file names had to be always escaped to prevent their expansion. The brace expansion code has been updated to take no action when the brace expansion option is turned off, and brace expansion in ksh can now be turned off and on as needed.
- Previously, ksh did not handle the reuse of low file descriptor numbers when they were not used for the standard input, output, or error output. As a consequence, when any of stdin, stdout, or stderr was closed and its file descriptor was reused in command substitution, the output from that substitution was empty. With this update, ksh has been updated to no longer reuse "low file descriptors" for command substitution. Command substitution in ksh now works correctly even if any of stdin, stdout or stderr is closed.
- Previously, ksh did not mask exit codes and sometimes returned a number that was too high and could be later interpreted as termination by a signal. Consequently, if ksh was started from the "su" utility and it exited with a high-number exit code, "su" incorrectly generated a core dump. To prevent confusion of a parent process, ksh has been updated to mask exit codes when terminating.
- Previously, after forking a process, ksh did not clear the argument list of the process properly. Consequently, when listing processes using the ps tool, the arguments field of the forked process could contain some old arguments. The code has been modified to always clear the unused space of the argument string, and the ps tool now prints correct arguments.
- Previously, ksh did not verify whether it had the execute permission for a given directory before attempting to change into it. Consequently, ksh always assumed it was operating inside that directory, even though the attempt to access the directory was in fact unsuccessful. With this update, ksh checks for the execute permission and reports an error as expected if the permission is missing.
- Ksh could set a wrong process group when running a script in monitor mode. As a consequence, when such a script attempted to read an input, the ksh process stopped the script. With this update, ksh has been fixed to use the correct process group and the script executes as expected in the described scenario.
Users of ksh are advised to upgrade to these updated packages, which fix these bugs.