Concurrent

A Bash function to run tasks in parallel and display pretty output as they complete.

Examples

Run three tasks concurrently:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1

Run three tasks sequentially:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --sequential

Start the medium task after the short task succeeds:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --require 'My short task'   \
    --before  'My medium task'

Start the short task after both other tasks succeed:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --require 'My long task'    \
    --require 'My medium task'  \
    --before  'My short task'

Same as above, but shorter:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --require-all --before 'My short task'

Start the medium task and the long task after the short task succeeds:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --require 'My short task'   \
    --before  'My medium task'  \
    --before  'My long task'

Same as above, but shorter:

concurrent \
    - 'My long task'   sleep 10 \
    - 'My medium task' sleep 5  \
    - 'My short task'  sleep 1  \
    --require 'My short task' --before-all

Run the first two tasks concurrently, and then the second two tasks concurrently, and then the final three tasks concurrently.

concurrent \
    - 'Task 1'  sleep 3 \
    - 'Task 2'  sleep 3 \
    --and-then \
    - 'Task 3'  sleep 3 \
    - 'Task 4'  sleep 3 \
    --and-then \
    - 'Task 5'  sleep 3 \
    - 'Task 6'  sleep 3 \
    - 'Task 7'  sleep 3

If your command has a - argument, you can use a different task delimiter:

concurrent \
    + 'My long task'   wget -O - ... \
    + 'My medium task' sleep 5  \
    + 'My short task'  sleep 1

You can display extra information at the end of each task's status line by echoing to fd 3.

my_task() {
    ...
    echo "(extra info)" >&3
    ...
}

Take a look at demo.sh for more involved examples.

Dry Run

If you have a lot of dependencies between tasks, it's generally a good idea to perform a dry-run to ensure that the tasks are ordered as expected. Set the CONCURRENT_DRY_RUN environment variable to perform a dry-run.

Failure Demo

Interrupted Demo

Requirements

• bash >= 4.2 (for declare -g)
• cat
• cp
• date
• mkdir
• mkfifo
• mktemp
• mv
• sed (gsed for OS X)
• tail
• tput

Change Log

• 2.1.0
  • New: New --and-then flag for dividing tasks into groups. All tasks in a group run concurrently, but all must complete before the next group may start (inspiration: fooshards on Reddit).
  • Fix: Removed extra backslashes in README (credit: bloody-albatross on Reddit)
• 2.0.1
  • Fix: kill is a bash builtin (credit: @ScoreUnder)
  • Fix: Require GNU sed on OS X (credit: @kumon)
  • Fix: Static analysis with shellcheck on push via Travis CI (credit: @xzovy)
  • Fix: Cleaner signal handling.
  • Fix: Simplified event loop.
• 2.0.0
  • New: Tasks can now display status updates by echoing to fd 3.
• 1.6.0
  • New: CONCURRENT_DRY_RUN environment variable runs sleep 3 instead of actual commands (and prints message).
• 1.5.2
  • Fix: Requirement loops disallowed.
• 1.5.1
  • Fix: Task is not allowed to require itself directly.
• 1.5.0
  • New: First argument is now the task delimiter.
• 1.4.1
  • Fix: Namespaced previously-missed function.
• 1.4.0
  • New: New --require-all and --before-all flags.
  • Fix: Namespaced all concurrent-related functions and variables.
  • Fix: Unsetting all concurrent-related functions and variables in the task's context.
  • Fix: Enforcing foreground in an interactive shell.
• 1.3.0
  • New: New --sequential flag, for when each task requires the previous.
• 1.2.0
  • New: Running tasks have an animated cursor.
  • Fix: Enforcing bash version 4.3.
  • Fix: Echo is re-enabled even if an internal error occurs.
• 1.1.6
  • Fix: Enforcing bash version 4.
• 1.1.5
  • Fix: Tasks now use original $PWD and $OLDPWD.
• 1.1.4
  • Fix: Tasks now use original $SHELLOPTS and $BASHOPTS.
• 1.1.3
  • Fix: Sanitizing forward slashes from log names.
• 1.1.2
  • Fix: Ensuring task status file exists even if an internal error occurs.
• 1.1.1
  • Fix: Task command may now have arguments starting with -.
• 1.1.0
  • New: Gracefully handling SIGINT.
  • Fix: Works on OS X too.
• 1.0.0
  • Initial working release.