Sigscan

List POSIX signal information for all processes.

Features

• Easy to use (just sigscan)
• Blazingly fast (~95% of time spent in kernel space)
• Uses colors if output is detected as a terminal that supports them (or forcibly with --(no-)colors).

Limitations

• Only classic POSIX signals are supported, no real-time signals.
• Relies on /proc and therefore only works on Linux.

Installation

sigscan is available for downloads as pre-compiled binaries or you can build it from source.

Download Released Binaries

You can find binaries on the releases page or tweak + run the code below in your shell to install it to your system.

# Pick a download target
ARCH="x86_64" # or aarch64, riscv64gc
LIBC=gnu # or musl
INSTALL_DIR="/usr/local/bin/"
LATEST_VERSION=$(curl -s https://raw.githubusercontent.com/brannondorsey/sigscan/refs/heads/main/Cargo.toml | grep -Po '^version = "\K[^"]*')

# Download and install it
curl -L "https://github.com/brannondorsey/sigscan/releases/download/v${LATEST_VERSION}/sigscan-${ARCH}-unknown-linux-${LIBC}.tar.gz" \
    | tar xz sigscan \
    && sudo mv sigscan "${INSTALL_DIR}"

# Verify installation
sigscan

From Source

# Install rustup, if you don't already have it
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Install sigscan
cargo install --path signal-scan

# Verify installation
sigscan

Examples

Basic usage

# Show all processes with caught, blocked, and pending signals (default)
sigscan

# Show only processes that are ignoring signals (omitted by default)
sigscan --ignored

# Show caught, blocked, pending, **and** ignored signals (equivalent to `sigscan -cbpi`)
sigscan --caught --blocked --pending --ignored

# Or use --all/-a instead of specifying all four signal types, plus processes with empty signal masks
sigscan --all

# Show only processes with totally empty signal masks (e.g. no signals are caught, blocked, pending, or ignored)
sigscan --empty

Recipes

sigscan subscribes to the Unix philosophy of doing one thing and doing it well. It can be combined with other tools to answer more complex questions.

# Paginate output
sigscan --color | less

# Show all signal info pertaining to a certain process
sigscan -cpbi --color | grep firefox

# Get PIDs of processes that are blocking any type of signal
sigscan --blocked | cut -d" " -f1

# Find potential daemon processes (catching SIGHUP)
sigscan --caught | grep HUP | cut -d" " -f2

# Get the full command line of processes that are catching TERM
sigscan --caught | grep TERM | cut -d" " -f1 | xargs ps -o pid,cmd

# Find processes that might be zombies (blocking SIGCHLD)
sigscan --blocked | grep CHLD | awk '{print $1}' | xargs ps -o pid,ppid,state,cmd

# Continuously watch for processes with pending signals
watch --color -n 0.1 "sigscan --pending --color"

Usage

$ sigscan --help
List POSIX signal information for all processes.

By default -c (--caught), -b (--blocked), and -p (--pending) are set.
However, any of these options you specify will override and reset the defaults.

Example: sigscan -cbp

Note: This tool only supports classic POSIX signals, not real-time signals
(e.g. SIGRTMIN and above).

Usage: sigscan [OPTIONS]

Options:
  -i, --ignored
          Show processes that are ignoring signals

  -c, --caught
          Show processes that are catching signals

  -b, --blocked
          Show processes that are blocking signals

  -p, --pending
          Show processes that have pending signals

      --cmdline
          Replace the binary name with the full value of /proc/$PID/cmdline surrounded by quotes

      --color
          Force enable colored output (can also be set via FORCE_COLOR env var)

      --no-color
          Force disable colored output (can also be set via NO_COLOR env var)

      --examples
          Print the examples section from the README

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version

License

sigscan is dual-licensed under either of:

• MIT license
• Apache License, Version 2.0

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.