Micro-embedded shell (QNX Neutrino)
The uesh utility provides a subset of the functionality found in the standard embedded shell, /bin/esh. You should find uesh useful for situations where memory requirements are limited. For example, you could use it to run a simple system initialization file for an embedded system.
The micro-embedded shell has some very significant limitations:
For applications that require greater functionality, use esh or the full shell, sh.
In uesh, command lines take this form:
command arg1 arg2 ... [redir-op file] [&]
|<file||redirect standard input from this file.|
|>file||redirect standard output to this file. If the file exists, it's overwritten; if the file doesn't exist, it's created.|
|>>file||redirect standard output to this file. If the file exists, the information is appended to the end of the file; if the file doesn't exist, it's created.|
|2>file||do the same as >file, but for standard error.|
|2>>file||do the same as >>file, but for standard error.|
|&||If a command contains an unquoted &, then uesh doesn't wait for the command to complete execution but immediately moves on to process the next command. The standard input of the command is redirected from /dev/null, and SIGINT and SIGQUIT are ignored.|
The uesh shell doesn't support filename expansion. Such shorthands as *.c for all files ended in .c don't work.
The following characters have a special meaning in uesh:
& \ " * ? [ space
To suppress the special meaning of these characters and keep their literal meaning, use quoting.
To quote a sequence of characters or sequence of words, enclose the sequence in double quotes. To quote a single character, use double quotes or precede it with the escape character (\).
represents a single, five-character argument.
You can keep the literal meaning of a double quote with the \ character. For example:
represents the single, five-character argument ab"cd.
The following commands are built into uesh. That is, uesh interprets and executes them internally.
Change the working directory of the current execution environment. If directory isn't specified, the value of the HOME environment variable becomes the new working directory.
exec [command [argument...]]
Execute a command and/or manipulate file descriptors.
The exec command opens, closes, or copies file descriptors as specified by any I/O redirections given as part of argument. If a command is specified, that command is spawned as a replacement for uesh. Any specified arguments are passed to the spawned process.
Cause uesh to exit with the exit status specified by n. If n isn't specified, uesh exits with the status of the last command executed.
export name[=word]... export -p
Mark environment variables for export, which causes them to be in the environment of subsequently executed commands. If you specify the -p option, the names and values of all exported variables are written to the standard output.
If PATH isn't in the existing environment when uesh is invoked, it's set to /bin:/usr/bin. For more information on setting PATH, see "Setting PATH and LD_LIBRARY_PATH" in the Configuring Your Environment chapter of the Neutrino User's Guide.
esh, fesh, ksh, rsh, sh
"Setting PATH and LD_LIBRARY_PATH" in the Configuring Your Environment chapter of the Neutrino User's Guide