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Shell Scripting Reference

The uniOS userspace shell supports basic scripting for diagnostics, automation, and system tasks.

Running Scripts

Scripts are plain text files containing shell commands. Run a script with:

run /data/startup.sh

You can also use source to run a script within the current shell context:

source diagnostics.sh

Lines starting with # are treated as comments.

Variables

Setting and Unsetting

Variables are session-local. Use set to define or update a variable:

set PATH=/bin
set OS_NAME=uniOS

To remove a variable:

unset OS_NAME

Accessing Variables

Prefix the variable name with $ to expand its value:

echo $PATH

The special variable $? contains the exit status of the previous command (0 for success, non-zero for error).

Conditionals

if blocks allow for basic branching.

if $STATUS == 0
    echo "Operation successful"
else
    echo "Operation failed"
endif

Supported operators:

  • String: ==, !=
  • Numeric: <, >, <=, >=

Loops

while blocks repeat execution as long as a condition is met.

# Example: Waiting for a file to appear
while ! stat /data/ready.txt
    sleep 500
end

Note

Variable increments are not natively supported in the current shell. Loops are primarily intended for polling or persistent diagnostic tasks.

Built-in Commands

The shell includes built-in support for:

  • File System: ls, cd, pwd, cat, touch, rm, mkdir, cp, mv.
  • System Info: mem, ps, uptime, date, uname, sysinfo, cpuinfo.
  • Networking: ping, resolve.
  • Process: kill, exec, reboot, poweroff.

Limits and Constraints

  • Variable Count: Max 32 variables per session.
  • Variable Length: Max 256 bytes per value.
  • Script Length: Max 256 lines.
  • Loop Iterations: Safety cap at 10,000 iterations.
  • Nesting: Max 16 levels of nested blocks.