Support for custom shells

It is now possible to override and explicitly specify the shell you
would like used when executing cron tasks. This is accomplished with the
NEXTCLOUD_EXEC_SHELL environment variable, which defaults to bash. You
can also override and customize the arguments provided to that shell
executable via NEXTCLOUD_EXEC_SHELL_ARGS, which defaults to "-c".

See documentation for more detail and examples.

Fixes #6

Dockerfile

@@ -6,6 +6,8 @@ ENV NEXTCLOUD_EXEC_USER=www-data
 ENV NEXTCLOUD_CONTAINER_NAME=
 ENV NEXTCLOUD_PROJECT_NAME=
 ENV NEXTCLOUD_CRON_MINUTE_INTERVAL=15
+ENV NEXTCLOUD_EXEC_SHELL=bash
+ENV NEXTCLOUD_EXEC_SHELL_ARGS=-c
 
 COPY scripts/*.sh /
 COPY scripts/cron-scripts /cron-scripts

README.md

@@ -77,6 +77,17 @@ how this all works.
   in the tasks being executed using the Nextcloud container's running user. Specifically, the
   `--user` option will *not* be provided to the `docker exec` command.
 
+* `NEXTCLOUD_EXEC_SHELL`<br>
+  Allows specifying a custom shell program that will be used to execute cron tasks inside the
+  Nextcloud container. This shell program *must* exist inside the Nextcloud container itself
+  (validation happens on start up to ensure this). The default value if not specified is `bash`.
+
+* `NEXTCLOUD_EXEC_SHELL_ARGS`<br>
+  Allows custom arguments to be passed to the shell program specified by `NEXTCLOUD_EXEC_SHELL`. See
+  the detailed documentation provided later on in this document for more information. At minimum,
+  the arguments passed to your shell program must allow for the execution of a series of string
+  commands. The default value if not specified is `-c`.
+
 * `DEBUG`<br>
   Enables more verbose logging in core scripts. Useful only for development. To get more verbose
   output in your own custom cron scripts, use `set -x` in the actual script.
@@ -103,15 +114,15 @@ in addition to the default `cron.php` task. To add your custom tasks, follow the
 1. Write a shell script that runs the commands that will be part of your task. This shell script
    must have the `.sh` extension. An example of the contents of such a script is below. As an
    optional security measure, do not make this shell script executable. The contents of the file are
-   piped into `bash`, so the executable bit is not used.
+   piped into `sh`, so the executable bit and shebang line are not used or required.
 
    ```sh
-   #!/usr/bin/env bash
    php -f /var/www/html/cron.php
    ```
 
-2. Mount this shell script inside the `/cron-scripts` directory. Here's an example if you're using
-   `docker-compose.yml`:
+2. Mount this shell script inside the `/cron-scripts` directory. You may also choose to *replace*
+   this directory, but bear in mind that you will not be running the built-in cron tasks in that
+   case. Here's an example if you're using `docker-compose.yml`:
 
    ```yml
    services:
@@ -139,11 +150,42 @@ services:
 As an optional safety measure, mount the directory or files as read-only (via the `:ro` at the end).
 The container should not modify the files, but it doesn't hurt to be explicitly strict.
 
+### Customizing the Shell
+
+By default, all cron task scripts in the `/cron-scripts` directory are executed with `bash`.
+However, not all Nextcloud containers have `bash`. In this case, you may want to override it with a
+shell like `sh`. You can accomplish this (as well as customizing the arguments passed to the shell)
+with `NEXTCLOUD_EXEC_SHELL` and `NEXTCLOUD_EXEC_SHELL_ARGS`.
+
+The shell args are used when passing the contents of script files to the shell executable inside the
+Nextcloud container. Customizing the args might be necessary depending on the shell program you
+choose, or you may want to leverage options for debugging purposes (See "Debugging" section for
+examples).
+
+> **NOTE**<br>
+> The arguments that are passed to the shell program must, at least, allow the execution of a string
+> of commands. See the documentation on your chosen shell for which arguments these should be.
+
+Here is an example of how you would override `bash` for `sh` using `docker-compose.yml` (again,
+greatly simplified for example purposes; this is not a complete YAML):
+
+```yml
+services:
+  cron:
+    image: rcdailey/nextcloud-cronjob
+    environment:
+    - NEXTCLOUD_EXEC_SHELL=sh
+    - NEXTCLOUD_EXEC_SHELL_ARGS=-c
+```
+
+Note that `-c` is the default for `NEXTCLOUD_EXEC_SHELL_ARGS`, so it isn't necessary to specify it
+above. However, it is explicitly specified for example purposes.
+
 ### Notes
 
 * All cron task shell scripts run at the same interval defined by `NEXTCLOUD_CRON_MINUTE_INTERVAL`.
 * Modification of your own shell scripts on the host do not require that you restart/recreate the
-  container.
+  container (only when volume mappings change in the YAML file).
 
 ## Debugging
 
@@ -161,3 +203,17 @@ Started crond
 > Running Script: run_cron_php.sh
 > Done
 ```
+
+You can leverage `NEXTCLOUD_EXEC_SHELL_ARGS` to get more verbose output from your scripts. For
+example, for `bash` you can specify `-x` for debug mode. So you could use this in your YAML:
+
+```yml
+services:
+  cron:
+    image: rcdailey/nextcloud-cronjob
+    environment:
+    - NEXTCLOUD_EXEC_SHELL_ARGS=-xc
+```
+
+Note the addition of `-x` in the arguments. This will provide line-by-line output for each cron task
+shell script executed.

scripts/cron-scripts/run-cron-php.sh

@@ -1,2 +1 @@
-#!/usr/bin/env bash
 php -f /var/www/html/cron.php

scripts/cron-tasks.sh

@@ -2,16 +2,12 @@
 set -e
 [[ ! -z "$DEBUG" ]] && set -x
 
+source /nextcloud-exec.sh
+
 echo "-------------------------------------------------------------"
 echo " Executing Cron Tasks: $(date)"
 echo "-------------------------------------------------------------"
 
-# If a user must be specified when executing the task, set up that option here.
-# You may also leave NEXTCLOUD_EXEC_USER blank, in which case it will not be used.
-if [[ -n "$NEXTCLOUD_EXEC_USER" ]]; then
-    exec_user="--user $NEXTCLOUD_EXEC_USER"
-fi
-
 # Obtain the ID of the container. We do this each iteration since the Nextcloud container may be
 # recreated while the cron container is still running. We will need to check for a new container ID
 # each time.
@@ -23,13 +19,17 @@ fi
 
 echo "> Nextcloud Container ID: ${containerId}"
 
+run_scripts_in_dir() {
+    cd "$1"
+    for script in *.sh; do
+        echo "> Running Script: $script"
+        nextcloud_exec "$containerId" "$(< $script)"
+    done
+}
+
 # Loop through all shell scripts and execute the contents of those scripts in the Nextcloud
 # container. It's done this way so that the user may mount more scripts to be executed in addition
 # to the default ones.
-cd /cron-scripts
-for script in *.sh; do
-    echo "> Running Script: $script"
-    docker exec $exec_user -i "$containerId" bash < $script
-done
+run_scripts_in_dir /cron-scripts
 
 echo "> Done"

scripts/entrypoint.sh

@@ -2,6 +2,8 @@
 set -e
 [[ ! -z "$DEBUG" ]] && set -x
 
+source /nextcloud-exec.sh
+
 if [[ -z "$NEXTCLOUD_CONTAINER_NAME" ]]; then
     echo "NEXTCLOUD_CONTAINER_NAME is a required variable"
     exit 1
@@ -24,6 +26,15 @@ else
     echo "Found Nextcloud container with ID $containerId"
 fi
 
+# Verify the chosen shell exists in the Nextcloud container
+if ! nextcloud_exec_no_shell "$containerId" sh -c "command -v \"$NEXTCLOUD_EXEC_SHELL\"" >/dev/null 2>&1
+then
+    echo "ERROR: Shell \"$NEXTCLOUD_EXEC_SHELL\" does not exist in the Nextcloud container"
+    exit 1
+else
+    echo "Chosen shell \"$NEXTCLOUD_EXEC_SHELL\" was found in the Nextcloud container"
+fi
+
 echo "*/$NEXTCLOUD_CRON_MINUTE_INTERVAL * * * * /cron-tasks.sh" \
     > /var/spool/cron/crontabs/root
 

scripts/nextcloud-exec.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+nextcloud_exec_no_shell() {
+    containerId="$1"; shift
+
+    # If a user must be specified when executing the task, set up that option here.
+    # You may also leave NEXTCLOUD_EXEC_USER blank, in which case it will not be used.
+    if [[ -n "$NEXTCLOUD_EXEC_USER" ]]; then
+        exec_user="--user $NEXTCLOUD_EXEC_USER"
+    fi
+
+    docker exec $exec_user -i "$containerId" "$@"
+}
+
+nextcloud_exec() {
+    containerId="$1"; shift
+    nextcloud_exec_no_shell "$containerId" "$NEXTCLOUD_EXEC_SHELL" $NEXTCLOUD_EXEC_SHELL_ARGS "$@"
+}

test/shell-test/docker-compose.yml

@@ -0,0 +1,20 @@
+version: '3'
+
+services:
+  app:
+    image: nextcloud:19-fpm-alpine
+
+  cronjob:
+    build: ../..
+    depends_on:
+      - app
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - /etc/localtime:/etc/localtime:ro
+    environment:
+      - NEXTCLOUD_PROJECT_NAME=shell-test
+      - NEXTCLOUD_CONTAINER_NAME=app
+      - NEXTCLOUD_CRON_MINUTE_INTERVAL=1
+      - NEXTCLOUD_EXEC_SHELL=sh
+      - NEXTCLOUD_EXEC_SHELL_ARGS=-xc
+      - DEBUG=1