How do anonymous pipes coordinate parent-child communication?

A strong answer

A strong candidate frames How do anonymous pipes coordinate parent-child communication? around the exact memory layout, compiler semantics, and hardware execution model covered in Inter-Process Streams: Anonymous Pipes and Named FIFOs. Explain pipe creation before fork, descriptor inheritance, closing unused ends, and EOF detection on read.

Signals are lightweight software interrupts, but they carry almost zero data: a standard signal informs a process that an event happened, but it cannot stream structured messages, lines of text, or binary payloads.

The parent writes "Hello World\n", calls close(fds[1]), and waits for the child. The child reads "Hello World\n", but never reaches "Child finished reading.\n". The process stalls permanently.

In a production interview, always connect the specification rule to its concrete runtime consequence: state what lives on the stack versus the heap or static storage segment, how the compiler or operating system validates alignments, lifetimes, and error codes, and what happens under adversarial or boundary inputs (such as zero-length buffers, integer overflow, concurrent mutation, or partial I/O). Backing your explanation with a small trace of register/memory state transitions immediately separates senior systems engineers from candidates who only memorized syntax.

What the interviewer is listening for

• Mastery of core invariant: Create unidirectional byte channels between related processes using pipe.
• Mastery of core invariant: Enforce descriptor closure hygiene in parent and child to signal End-Of-File (EOF).
• Mastery of core invariant: Handle SIGPIPE signals and EPIPE errors when writing to orphan streams.
• Hardware and ABI awareness: Explaining how sizes, alignments, calling conventions, or kernel boundaries behave on real 64-bit targets rather than relying on implementation-defined assumptions.
• Defensive engineering: Naming the exact compiler flags (-Wall -Wextra -Werror), static analyzers, or runtime sanitizers (-fsanitize=address,undefined,thread) that verify correctness in CI.

Common mistakes

• Explaining only surface syntax without tracing the underlying memory addresses, ownership lifetime, or kernel/user-space state transitions.
• Assuming undefined behavior (such as signed overflow, uninitialized reads, strict-aliasing violations, or dangling pointers) will "just work" because it passed an unoptimized -O0 debug build.
• Ignoring return codes, partial reads/writes, alignment padding, or cleanup paths when an allocation or syscall fails midway through a function.