Loading page
About this tool
Look up what a shell or process exit code means, including 128+N signal deaths, sysexits.h codes and Docker OOM kills.
This explorer decodes any process exit code from 0 to 255 into its meaning — POSIX shell conventions (126 not executable, 127 not found), the BSD sysexits.h EX_* block (64–78), and the 128+N rule that turns a signal death into a code, so 137 is decoded as 128 + SIGKILL(9). It is built for developers and SREs staring at echo $?, a failed CI step or a crashed container status and needing the cause in one lookup.
Open Exit Code Reference Explorer on AltFTool — it loads instantly in your browser.
Paste your code or data sample into the workspace.
Pick the format, conversion, or analysis you need.
Copy the polished result straight back into your project.
Any code above 128 is decomposed into 128 + N and named from the Linux signal table.
Codes like 137, 139 and 143 include what they mean specifically in Docker and Kubernetes.
Enter exit(-1) or exit(300) and the tool shows the wrapped mod-256 value the shell actually reports.
Exit code 137 means the process was killed by SIGKILL (signal 9), because shells report death-by-signal-N as 128 + N and 128 + 9 = 137. In Docker and Kubernetes it almost always indicates the kernel OOM killer terminated the container for exceeding its memory limit — check kubectl describe pod for an OOMKilled reason.
127 means the shell could not find the command at all — a typo or a binary missing from PATH — while 126 means the command was found but could not be executed, usually a missing execute permission bit or a binary built for the wrong architecture. Both are defined by POSIX shell behaviour.
Exit code 139 is a segmentation fault: 128 + 11, where signal 11 is SIGSEGV. The program accessed memory it was not allowed to touch — a bug in the binary or a native library, not in the shell or container runtime.
255. POSIX defines the exit status as one unsigned byte, so values outside 0–255 wrap modulo 256 — exit(-1) reports 255 and exit(256) reports 0. If your program needs to convey more than that, write to stderr or a file instead of overloading the status byte.