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The Bash source command reads commands into the current shell environment. Running a script as a separate process has a different boundary. That distinction matters when a file sets variables, functions or shell options.
Distinguish sourcing from separate execution
In Bash, source and the dot command execute a file in the current shell context. Running bash file.sh starts a separate Bash process instead. Variables set only in that child process do not automatically become variables in the parent shell.
Review the file before sourcing it
A sourced file is not merely a passive configuration document; it can contain executable commands. Review it as carefully as a script and use an explicit path such as source ./sample.sh. Do not source untrusted content or files that expose private credentials.
Check lasting effects on the current session
Sourcing can change variables, functions, shell options and even the working directory. Test in a disposable shell when uncertain. An exit command in sourced content can end the current shell, so a file written for standalone execution may be unsuitable for sourcing without review.
A practical checklist
- Confirm why the current shell must change.
- Review every command in the file.
- Use a clear path to the intended file.
- Test in a disposable shell when uncertain.
- Inspect variables, options and directory afterward.
Worked example
Illustrative example: a reviewed sample sets DEMO_LABEL=preview and defines a harmless printing function. Sourcing it makes both available in the current shell. Running the same file in a separate Bash process does not leave that function behind in the parent session.
Common questions
Is source a way to read arbitrary text safely? No; it executes commands. Does sourcing always create a new process? No. Can a sourced script alter the current directory? Yes, if it contains commands that do so.
What to do next
Keep environment setup files small and understandable. Use separate execution when persistent changes to the current shell are not required.
Sources and further reading
Related reading
- How to Document a Software Installation for Nontechnical Users
- How to Protect Client Secrets in Development Workflows
Identify Your Linux Shell: Current Process Versus Login Default
Find Your Current Directory in Bash Before Using Relative Paths