doc: Document passing input into stdin.

* doc/ccwl.skb (Tutorial)[Passing input into the standard input stream
of a command]: New section.
* doc/pass-stdin.scm, doc/pass-stdin.out: New files.

3 files changed, 35 insertions, 0 deletions

diff --git a/doc/ccwl.skb b/doc/ccwl.skb
index 51ce5bf..2fec996 100644
--- a/doc/ccwl.skb
+++ b/doc/ccwl.skb
@@ -149,6 +149,21 @@ output.])
 
       (prog :line #f (source :file "doc/capture-output-file-with-parameter-reference.out")))
 
+    (section :title [Passing input into the standard input stream of a command]
+      (p [Some commands read input from their standard input
+stream. Let us do that from ccwl. The workflow below reports the size
+of a file by passing it into the standard input of
+,(command "wc"). Notice the additional ,(code "#:stdin") keyword that
+references the input ,(code "file").])
+
+      (scheme-source "doc/pass-stdin.scm")
+
+      (p [Compiling and running this workflow gives us the following
+output. Notice the file ,(file "foo") passed into the standard input
+of ,(command "wc"), and the file size reported in bytes.])
+
+      (prog :line #f (source :file "doc/pass-stdin.out")))
+
     (section :title [Workflow with multiple steps]
       (p [Till now, we have only written trivial workflows with a
 single command. If we were only interested in executing single
diff --git a/doc/pass-stdin.out b/doc/pass-stdin.out
new file mode 100644
index 0000000..c4af7da
--- /dev/null
+++ b/doc/pass-stdin.out
@@ -0,0 +1,13 @@
+$ ccwl compile pass-stdin.scm > pass-stdin.cwl
+$ cwltool pass-stdin.cwl --file foo
+     [workflow ] start
+     [workflow ] starting step count-bytes
+     [step count-bytes] start
+     [job count-bytes] /tmp/wxi6_9jz$ wc \
+    -c < /tmp/siden6hu/stg51eaae41-52a5-4e69-a78e-caefd84f7af5/foo
+37
+     [job count-bytes] completed success
+     [step count-bytes] completed success
+     [workflow ] completed success
+{}
+     Final process status is success
\ No newline at end of file
diff --git a/doc/pass-stdin.scm b/doc/pass-stdin.scm
new file mode 100644
index 0000000..3bdc70b
--- /dev/null
+++ b/doc/pass-stdin.scm
@@ -0,0 +1,7 @@
+(define count-bytes
+  (command #:inputs (file #:type 'File)
+           #:run "wc" "-c"
+           #:stdin file))
+
+(workflow ((file #:type File))
+  (count-bytes #:file file))