Core · Module 5 · Lesson 11 of 12
System Call Errors, errno, and EINTR
Turn failed POSIX calls into reliable control flow by reading errno, distinguishing transient failures, and retrying operations safely.
Pro — members onlyAbout 15 minutes
By the end you can
- Explain how POSIX functions report failure
- Use errno only after a call reports failure
- Handle EINTR without duplicating completed work
- Preserve useful error context for callers and users
Builds on File Handling with Standard I/O.
01 · A question first
A system call can fail even when the file, socket, or process is valid. How can a program tell whether it should retry, change its input, or stop immediately?
Make a guess before you read on.
02 · The idea
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What's inside
- Start with the problem
- Read the result before the reason
- Classify errors instead of retrying everything
- Handle EINTR without duplicating work
- Preserve context across layers
- What this costs
- Where it is used
- Operational checklist
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