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sshp - Parallel SSH Executor

sshp manages multiple ssh processes and handles coalescing the output to the terminal. By default, sshp will read a file of newline-separated hostnames or IPs and fork ssh subprocesses for them, redirecting the stdout and stderr streams of the child line-by-line to stdout of sshp itself.

Installation

Pull the source code and run make to compile sshp:

$ make
cc -o src/fdwatcher.o -c -D USE_KQUEUE=0 -Wall -Werror -Wextra -Wpedantic -O2 src/fdwatcher.c
cc -o sshp -Wall -Werror -Wextra -Wpedantic -O2 src/sshp.c src/fdwatcher.o
$ ./sshp -v
v1.0.0

Then optionally run make install to install sshp:

$ sudo make install
cp man/sshp.1 /usr/local/man/man1
cp sshp /usr/local/bin
$ sshp -v
v1.0.0

sshp requires a kernel that supports epoll or kqueue to run. This has been tested on Linux, illumos, MacOS, and FreeBSD.

About

sshp has 3 modes of execution:

  • line mode (line-by-line output, default).
  • group mode (grouped by hostname output, -g).
  • join mode (grouped by unique output, -j).

The first 2 modes, line and group, operate in largely the same way, differing only in how data is buffered from the child processes and printed to the screen. Line mode buffers the data line-by-line, whereas group mode does no buffering at all and prints the data once it is read from the child.

The last mode, join, however, buffers all of the data from all of the child processes and outputs once all processes have finished. Instead of grouping the output by host, it is grouped by the output itself to show which hosts had the same output.

Examples

Given the following hosts file called hosts.txt:

# example hosts file

arbiter.rapture.com
cifs.rapture.com
decomp.rapture.com

Parallel ssh into hosts supplied by a file running uname -v:

line-by-line

Pass in -e to get the exit codes of the commands on the remote end. The local exit code will be 0 if all ssh processes exit successfully, or 1 if any of the ssh processes exit with a failure:

exit-codes

Also note that the hosts file can be passed in via stdin if -f is not supplied.

Run with -d to get debug information making it clear what sshp is doing:

debug-id

Run with -g (group mode) to group the output by hostname as it comes in. To illustrate this, -m is set to 1 to limit the maximum number of concurrent child processes to 1, effectively turning sshp into an ssh serializer:

serialize-group

Run with -j (join mode) to join the output by the output itself and not the hostname:

join-mode

Send the sshp process a SIGSUR1 signal to print out process status information while it is running. In this example, a signal was sent twice to the process:

sigusr1-status

Tips and Tricks

If one or more of the hosts you want to ssh into are not in your known_hosts file it can be really overwhelming to get all of the warning messages / prompts to save the host key. You can manually accept any new keys 1-by-1 with:

sshp -f hosts.txt -m 1 true

Or, accept all keys without any confirmation or validation (use at your own risk):

sshp -f hosts.txt -o StrictHostKeyChecking=no true

Exit Codes

  • 0 Everything worked and all child processes exited successfully.
  • 1 Everything worked, but 1 or more children exited with a non-zero code.
  • 2 Incorrect usage - the user supplied something incorrect preventing sshp from being able to run (unknown options, invalid host file, etc.).
  • 3 Program failure - the program experienced some failing in the system preventing sshp from being able to run (malloc failure, epoll failure, etc.).
  • 4 sshp killed by SIGTERM or SIGINT.
  • * Anything else - probably a blown assertion.

Usage

$ sshp -h
        _
  _____| |_  _ __     Parallel SSH Executor (v1.1.0)
 (_-<_-< ' \| '_ \    Source: https://github.com/bahamas10/sshp
 /__/__/_||_| .__/    Compiled: Jun  2 2021 12:23:56 (using kqueue)
            |_|       MIT License

Parallel ssh with streaming output.

USAGE:
    sshp [-m maxjobs] [-f file] command ...

EXAMPLES:
    ssh into a list of hosts passed via stdin and get the output of uname -v.

      sshp uname -v < hosts

    ssh into a list of hosts passed on the command line, limit max parallel
    connections to 3, and grab the output of pgrep.

      sshp -m 3 -f hosts.txt pgrep -fl process

    Upgrade packages on all hosts in the list one-by-one, grouping the output
    by host, with debugging output enabled.

      sshp -m 1 -f hosts.txt -d -g pkg-manager update

OPTIONS:
  -a, --anonymous            Hide hostname prefix, defaults to false.
  -c, --color <on|off|auto>  Set color output, defaults to auto.
  -d, --debug                Enable debug info, defaults to false.
  -e, --exit-codes           Show command exit codes, defaults to false.
  -f, --file <file>          A file of hosts separated by newlines, defaults to stdin.
  -g, --group                Group output by hostname (group mode).
  -h, --help                 Print this message and exit.
  -j, --join                 Join hosts together by output (join mode).
  -m, --max-jobs <num>       Max processes to run concurrently, defaults to 50.
  -n, --dry-run              Don't actually execute subprocesses.
  -s, --silent               Silence all output subprocess stdio, defaults to false.
  -t, --trim                 Trim hostnames (remove domain) on output, defaults to false.
  -v, --version              Print the version number and exit.
  -x, --exec <prog>          Program to execute, defaults to ssh.
  --max-line-length <num>    Maximum line length (in line mode), defaults to 1024.
  --max-output-length <num>  Maximum output length (in join mode), defaults to 8192.

SSH OPTIONS: (passed directly to ssh)
  -i, --identity <ident>     ssh identity file to use.
  -l, --login <name>         The username to login as.
  -o, --option <key=val>     ssh option passed in key=value form.
  -p, --port <port>          The ssh port.
  -q, --quiet                Run ssh in quiet mode.

MORE:
    See sshp(1) for more information.

Tests and Style

sshp comes with a very simple test suite. It checks for just basic usage and sanity. It can be run with make test:

$ make test
cd test && ./runtest test_*
running:  ./test_00_usage
sshp -v  is 0 ... ok
sshp -h  is 0 ... ok
sshp  is 2 ... ok
sshp -f / cmd  is 2 ... ok
sshp -f /should-not-exist cmd  is 2 ... ok
sshp -f /dev/null cmd  is 2 ... ok
sshp -f ./assets/hosts/empty-hosts.txt cmd  is 2 ... ok
sshp -m  is 2 ... ok
sshp -m 0  is 2 ... ok
sshp -m foo  is 2 ... ok
sshp -m -17  is 2 ... ok
sshp -g -j  is 2 ... ok
sshp -n -f ./assets/hosts/simple-hosts.txt cmd  is 0 ... ok
sshp -n -f - cmd  is 0 ... ok
sshp -n cmd  is 0 ... ok
sshp -n -f ./assets/hosts/long-hosts-good.txt cmd  is 0 ... ok
sshp -n -f ./assets/hosts/long-hosts-bad.txt cmd  is 2 ... ok

running:  ./test_10_exec
sshp -x ./assets/cmd/true arg  is 0 ... ok
sshp -x ./assets/cmd/true -j arg  is 0 ... ok
sshp -x ./assets/cmd/true -g arg  is 0 ... ok
sshp -x ./assets/cmd/false arg  is 1 ... ok
sshp -x ./assets/cmd/false -j arg  is 1 ... ok
sshp -x ./assets/cmd/false -g arg  is 1 ... ok
sshp -x ./assets/cmd/hello -a arg code  is 0 ... ok
sshp -x ./assets/cmd/hello -a arg stdout  is hello ... ok

running:  ./test_20_signals
../sshp -x ./assets/cmd/sleep arg TERM code  is 4 ... ok
../sshp -x ./assets/cmd/sleep arg INT code  is 4 ... ok

Style can be checked with make check, this does not require the program to be compiled:

$ make check
./test/check src/*.h src/*.c test/* man/*.md
checking:  src/fdwatcher.h
checking:  src/fdwatcher.c
checking:  src/sshp.c
checking:  test/check
checking:  test/hosts.txt
checking:  test/test
checking:  man/sshp.md

The style check is very simple. It ensures:

  1. No line exceeds 80 columns.
  2. No consecutive blank lines.
  3. Consistent use of tabs and spaces.

Comparison to Node.js sshp

This program was originally written in Node.js and released as node-sshp. This C variant is mostly compatible with the original Node.js version with some slight alterations:

  • -b has been changed to -c off (disable color output).
  • -N has been removed in favor of -o StrictHostKeyChecking=no.
  • -o has been added to allow for any ssh option to be passed in.
  • -u has been removed (not applicable without npm).
  • -y has been removed in favor of -o RequestTTY=force.

For more information on why sshp was ported from JavaScript to C, see this blog post.

License

MIT License