{"id":"c74b8de145647e5e","repo":"BurntSushi/ripgrep","slug":"could-not-find-nul-terminator-in-hostname","errorCode":null,"errorMessage":"could not find NUL terminator in hostname","messagePattern":"could not find NUL terminator in hostname","errorType":"console","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/cli/src/hostname.rs","lineNumber":70,"sourceCode":"        return Err(io::Error::new(io::ErrorKind::Other, msg));\n    };\n    // maxlen here includes the NUL terminator.\n    let mut buf = vec![0; maxlen];\n    // SAFETY: The pointer we give is valid as it is derived directly from a\n    // Vec. Similarly, `maxlen` is the length of our Vec, and is thus valid\n    // to write to.\n    let rc = unsafe {\n        libc::gethostname(buf.as_mut_ptr().cast::<libc::c_char>(), maxlen)\n    };\n    if rc == -1 {\n        return Err(io::Error::last_os_error());\n    }\n    // POSIX says that if the hostname is bigger than `maxlen`, then it may\n    // write a truncate name back that is not necessarily NUL terminated (wtf,\n    // lol). So if we can't find a NUL terminator, then just give up.\n    let Some(zeropos) = buf.iter().position(|&b| b == 0) else {\n        let msg = \"could not find NUL terminator in hostname\";\n        return Err(io::Error::new(io::ErrorKind::Other, msg));\n    };\n    buf.truncate(zeropos);\n    buf.shrink_to_fit();\n    Ok(OsString::from_vec(buf))\n}\n\n#[cfg(test)]\nmod tests {\n    use super::*;\n\n    #[test]\n    fn print_hostname() {\n        println!(\"{:?}\", hostname().unwrap());\n    }\n}\n","sourceCodeStart":52,"sourceCodeEnd":86,"githubUrl":"https://github.com/BurntSushi/ripgrep/blob/3fce3b5bb0236da2df6d99672afb8a719642eca7/crates/cli/src/hostname.rs#L52-L86","documentation":"After a successful libc::gethostname call, POSIX permits the returned buffer to lack a NUL terminator when the hostname was truncated to fit the buffer. This code scans the buffer for the first 0 byte; if none exists it refuses to guess and returns this error. It guards against returning garbage bytes as the hostname.","triggerScenarios":"The system's real hostname is longer than the value reported by _SC_HOST_NAME_MAX, gethostname writes a full buffer with no terminator, and buf.iter().position(|&b| b == 0) returns None.","commonSituations":"A hostname that was lengthened after sysconf was queried, a container with an unusually long FQDN exceeding the kernel's max, or a libc/POSIX-compliance quirk. Extremely rare in practice.","solutions":["Shorten the system hostname so it fits within _SC_HOST_NAME_MAX and is NUL-terminated.","Restart the process/kernel so sysconf and the actual hostname agree.","Fall back to reading the hostname from /etc/hostname or an env var instead of calling hostname()."],"exampleFix":null,"handlingStrategy":"fallback","validationCode":null,"typeGuard":null,"tryCatchPattern":"let host = match grep_cli::hostname() {\n    Ok(n) => n,\n    Err(_) => std::env::var(\"HOSTNAME\").map(Into::into).unwrap_or_default(),\n};","preventionTips":["Keep the system hostname shorter than _SC_HOST_NAME_MAX.","Provide an env-based fallback for robustness in containers.","Surface but do not panic on this rare error; it indicates a system oddity, not a bug in your code."],"tags":["hostname","unix","posix","nul-terminator"],"analyzedSha":"3fce3b5bb0236da2df6d99672afb8a719642eca7","analyzedAt":"2026-08-06T01:39:05.073Z","schemaVersion":2}