Commands

Tacoscript allows to you wrap shell commands and additionally add conditions and templated content. Multiple steps of a task can be tied together by defining dependencies.

The task cmd.run executes an arbitrary command in a shell of a host system. It has following syntax:

create-file:
  cmd.run:
    - name: echo 'data to backup' >> /tmp/data2001-01-01.txt
backup-data:
  cmd.run:
    - names:
        - tar czf /tmp/data2001-01-01.txt.tar.gz /tmp/data2001-01-01.txt
        - md5sum /tmp/data2001-01-01.txt.tar.gz >> /tmp/data2001-01-01.txt.tar.gz.md5
    - cwd: /tmp
    - require:
        - create-file
    - creates:
        - /tmp/data2001-01-01.txt.tar.gz
    - env:
        - PASSWORD: bunny
    - shell: bash
    - unless: service backup-runner status
    - onlyif: date +%c|grep -q "^Thu"

You can interpret this script as following:

The desired state of the script ‘create-file’ is a file at /tmp/data2001-01-01.txt. To achieve it, the tacoscript binary will execute a task of type ‘cmd.run’. This task type executes command echo 'data to backup' >> /tmp/data2001-01-01.txt in the shell of the host system. The second desired state of the script ‘backup-data’ is creation of 2 files: /dumps/data2001-01-01.txt.tar.gz and its md5 sum file at /dumps/data2001-01-01.txt.tar.gz.md5.

This will be achieved by executing a task of type ‘cmd.run’ which requires 2 shell commands:

• tar czf /dumps/data2001-01-01.txt.tar.gz /tmp/data2001-01-01.txt
• md5sum /dumps/data2001-01-01.txt.tar.gz >> /dumps/data2001-01-01.txt.tar.gz.md5

The commands will be executed in the following context:

• current working directory (cwd) will be /tmp
• env variables list will contain PASSWORD with value bunny
• as shell bash will be selected

Both commands will be only executed after create-file script. So the tacoscript interpreter will make sure that the create-file script is executed before backup-data and only if it was successful.

The commands will be executed only under the following conditions:

• The file /tmp/data2001-01-01.txt.tar.gz should be missing (to avoid data overriding)
• The service service backup-runner should not be running
• Today is Thursday

Either name or names (see below) is required.

create-file:
  cmd.run:
    - name: echo 'data to backup' >> /tmp/data2001-01-01.txt

Name describes a single executable command. In the example above the tacoscript interpreter will run echo 'data to backup' >> /tmp/data2001-01-01.txt command.

Either name or names (see above) is required.

backup-data:
  cmd.run:
    - names:
        - tar czf /dumps/data2001-01-01.txt.tar.gz /tmp/data2001-01-01.txt
        - md5sum /dumps/data2001-01-01.txt.tar.gz >> /dumps/data2001-01-01.txt.tar.gz.md5

Name contains the list of commands. All commands in the task will be executed in the order of appearance. If one fails, the whole execution will stop. All commands inside one task will be executed in the same context, which means in the current working directory, with same env variables, in the same shell and under same conditions.

If you want to change context of a command (e.g. use another shell), you should create another task e.g.

backup-data1:
  cmd.run:
    - name: mycmd in shell 'bash'
    - shell: bash
backup-data2:
  cmd.run:
    - name: mycmd in shell 'sh'
    - shell: sh

The names parameter with a single value has the same meaning as name field.

optional string change the working directory before command execution

backup-data:
  cmd.run:
    - cwd: /tmp

The cwd parameter gives the current working directory of a command. This value is quite useful if you want to use relative paths of files that you provide to your commands.

For example imagine following file structure:

C:\Some\Very\Long\Path
  someData1.txt
  someData2.txt

You want to pack someData1.txt and someData2.txt with the zip.exe binary. You can do it with the script as:

backup-data:
  cmd.run:
    - names:
        - tar.exe -a -c -z -f C:\Some\Very\Long\Path\someData1.txt.tar.gz C:\Some\Very\Long\Path\someData1.txt
        - tar.exe -a -c -z -f C:\Some\Very\Long\Path\someData2.txt.tar.gz C:\Some\Very\Long\Path\someData2.txt

Obviously we have quite long strings here. You can also change your working directory and use relative paths to get the same result:

backup-data:
  cmd.run:
    - cwd: C:\Some\Very\Long\Path\
    - names:
        - tar.exe -a -c -z -f someData1.txt.tar.gz someData1.txt
        - tar.exe -a -c -z -f someData2.txt.tar.gz someData2.txt

Specify a shell for the command execution.

Shell is a program that takes commands from input and gives them to the operating system to perform. Known Linux shells are bash, sh, zsh etc. Windows supports cmd.exe shell.

If you don’t specify this parameter, tacoscript will use the default golang exec function which intentionally does not invoke the system shell and does not expand any glob patterns or handle other expansions, pipelines, or redirections typically done by shells.

To expand glob patterns, you must specify the shell parameter, in this case you should take care to escape any dangerous input.

Note that if you use cmd.run task type without the shell parameter, usual patterns like pipelines and redirections won’t work.

If you specify a shell parameter, tacoscript will run your task commands as a ‘-c’ parameter under Unix and ‘/C’ parameter under Windows:

The script below:

 backup-data:
   cmd.run:
   - names:
     - touch serviceALock.txt
     - tar cvf somedata.txt.tar somedata.txt
     - rm serviceALock.txt
   - shell: bash

will run as:

bash -c touch serviceALock.txt
bash -c tar cvf somedata.txt.tar somedata.txt
bash -c rm serviceALock.txt

The script below:

 backup-data:
   cmd.run:
   - name: date.exe /T > C:\tmp\my-date.txt
   - shell: cmd.exe

will run as:

cmd.exe \C date.exe /T > C:\tmp\my-date.txt

Specify a user for command execution.

create-user-file:
  cmd.run:
    - user: www-data
    - touch: data.txt>

The user parameter allows to run commands as a specific user. In Linux systems this will require sudo rights for the tacoscript binary. In Windows this command will be ignored. Switching users allows to create resources (file, services, folders etc) with the ownership of the specified user.

After running the above script, tacoscript will create a data.txt file with the ownership of www-data user.

    sudo tacoscript tacoscript.yaml
    ls -la
    #output will be
    -rw-r--r--    4 root  root          128 Jul 15  2019 tacoscript.yaml
    -rw-r--r--    1 root  root          3550 Oct 30  2019 tacoscript
    -rw-r--r--@   1 www-data  www-data  0 Apr 23 09:22 data.txt

Specify environment variables available during command execution.

save-date:
  cmd.run:
    - name: psql
    - env:
        - PGUSER: bunny
        - PGPASSWORD: bug

The env parameter is a list of key value parameters where key represents the name of an environment variable and value its content. Env variables are parameters which are set from the outside of a running program and can be used as configuration data.

In this example the psql will read login and password from the corresponding env variables and connect to the database without any input parameters or configuration data.