C Shell

KosmicTask Help

C Shell

The C shell is a legacy shell. It is included for completeness and to provide legacy support for older shell scripts.

Calling the Task Run Function

Arguments are passed to C shell powered tasks as direct parameters rather than through a named entry point function. The task parameters will be forwarded to the task script as command line arguments.

Result Objects

The C shell returns results to the client by printing to stdout.

To return structured data, including the contents of files, C shell powered tasks should format result data using YAML.

KosmicTask supports both the YAML inline and block formats.

# return a YAML block format array
echo "---"
echo "- Mercury"
echo "- Venus"
echo "- Earth"
echo "- Mars"
echo "- Jupiter"
echo "- Saturn"
echo "- Uranus"
echo "- Neptune"

Inline format.

# return a YAML inline format dictionary
set item1 = "item 1"
set item2 = "item 2"

echo "---"
echo "{key1: $item1, key2: $item2}"

Result File Handling

KosmicTask supports the returning of file contents within task results.

KosmicTask automatically looks for a kosmicFile record containing file paths within a dictionary type result object. If found, KosmicTask will return the contents of the file or files to the client.

For C shell powered tasks files are returned as results using the following YAML dictionary syntax:

set file="capture.png"
echo "---"
echo "{kosmicFile: $file}"

A common usage scenario is that a task creates a temporary file (or files) whose contents are then returned to the client. KosmicTask therefore supports automatic temporary file creation and deletion. Temporary files created through KosmicTask are automatically deleted once the parent task has completed.

C shell powered tasks can create temporary files simply by creating files in the current working directory.

# capture screen image to file
# files created in the current directory will be deleted when the task ends
set file="capture.png"

# capture screen
screencapture -t png $file

# YAML document header
echo "---"

# return a YAML inline format dictionary
echo "{kosmicFile: $file, kosmicInfo: file returned}"

Logging and Debugging

Diagnostic and logging information can be written to a task's error stream on /dev/stderr.

# send log value to stderr
echo "Goodbye, kosmos!" >/dev/stderr