Linux orientation

Explanation

Why an RTL or DV engineer uses Linux

Linux is the working environment around most semiconductor tools. You use it to organize RTL and testbench files, configure tool paths, compile a design, run simulations, inspect logs, start regressions, and preserve results. You do not need to become a system administrator before doing this work. You need to understand the command line and verify what each command did.

Terminal, shell, and kernel

These names describe different parts of the environment:

When a terminal shows a prompt such as $, type the command after the prompt. Do not type the $ character shown in documentation.

How to read a command

A command normally has a command name followed by options and arguments:

command  option  argument
ls       -l      rtl/

• ls is the program to run.
• -l requests a detailed listing.
• rtl/ is the directory on which ls should operate.

Spaces separate these parts. Quotes keep a path containing spaces together as one argument.

Input, output, errors, and status

Every command can use three standard streams:

After a command finishes, Bash stores its exit status in $?. Status 0 normally means success. A nonzero value means the command reported a condition or failure that must be checked.

Getting help

cd is a Bash built-in, so help cd is more useful than looking for a separate executable. A missing optional tool is a valid finding; do not install software or use sudo unless the lab explicitly authorizes it.

Worked example

Run the following read-only checks:

cat /etc/os-release
uname -r
printf 'shell=%s\n' "$SHELL"
type printf
command -v bash
printf '%s\n' 'Linux setup check complete'
printf 'last-status=%s\n' "$?"

What to look for:

1. cat /etc/os-release identifies the distribution.
2. uname -r prints the running kernel release.
3. $SHELL shows the configured login shell.
4. type printf explains how the current shell resolves printf.
5. command -v bash prints the Bash executable path.
6. The final status should be 0 because the preceding printf succeeded.

Now observe a controlled failure:

ls /path-that-does-not-exist
printf 'ls-status=%s\n' "$?"

ls writes a diagnostic and returns a nonzero status. Capture $? immediately because the next command replaces it.

EDA connection

Use the same check before running a simulator:

command -v iverilog
printf 'lookup-status=%s\n' "$?"

If the tool is unavailable, report that result. Do not invent a successful run or download an unapproved binary.

Common mistakes

• Typing the documentation prompt character as part of the command.
• Copying a command without checking its arguments and current directory.
• Assuming that visible output means success without checking the exit status.
• Using sudo to hide a path, permission, or installation problem.
• Mixing Bash syntax with examples written for C shell or another shell.

Check yourself

What does $? contain? Why must you read it immediately after the command you want to check?