The type of a Genspio expression.

Abstract type to encode arbitrary byte-arrays in the EDSL as byte_array t values, OCaml literal strings or the outputs (as in stdout) of processes are byte-arrays.

Abstract type to encode NUL-terminated strings in the EDSL as c_string t values. C-strings cannot contain the '\x00' character. The command line arguments of commands as well as the contents of environment variables must be C-strings.

Create a c_string literal.

string is an alias for function:c_string.

Create a byte_array literal.

Add a “comment” string to an expression (will be displayed in error messages happening inside the expression).

"Some comment" %%% expr is an alias for comment "Some comment" expr.

Call a command from its list of “arguments” (including the first argument being the actual command).

Like call but with string literals; i.e. exec ["a"; "b"] is actually call [string "a"; string "b"] which is the usual shell command "a b" (with proper escaping).

Get the value of an environment variable as a string; it returns the empty string when the variable is not defined. If the argument is not a valid variable name, behavior is undefined.

Set the value of an environment variable as a string; it returns the empty string is the variable is not defined.

If the ~var argument is not a valid variable name or if the value does not fit in a shell variable (e.g. newlines), behavior is undefined.

Also, the total environment of a UNIX process counts towards the total size of the arguments passed on to a sub-process (see usually the result of "getconf ARG_MAX"). Genspio does not check for that limit which is not that high in some operating systems (e.g. about 200 KiB on the MacOSX Sierra that the Travis CI runs …). You might prefer putting or accumulating things in a tmp_file.

Check the return value of a command/expression/script.

succeeds expr is equivalent to returns expr ~value:0.

Check whether a file exists, i.e. a shortcut for call [c_string "test"; c_string "-f"; path] |> succeeds.

Conversions of the bool t type.

Functions on int t values (arithmetic, comparisons, conversions, etc.).

Functions on 'a list t values.

The silent “no-operation.”

Sequence a list of expressions into an expression.

Build a while loop.

loop_seq_while condition body is a shortcut for loop_while condition ~body:(seq body).

if_seq c ~t ~e is an alternate API for if_then_else (when ?e is provided) or if_then (otherwise) that takes “then” and “else” bodies which are lists for the seq construct.

Create a switch statement from a list of case and optionally a default (the function raises an exception if there are more than one default cases).

Create a normal case for a switch statement.

Create the default case for a switch statement.

Abstract type of file-descriptor redirections.

Create a file-descriptor to file-descriptor redirection.

Create a file-descriptor to file redirection.

Run a unit t expression after applying a list of file-descriptor redirections.

The redirections are applied in the list's order (which means they can be more easily followed in reverse order), see the “Arbitrary Redirections” example.

Invalid cases, like redirecting to a file-descriptor has not been opened, lead to undefined behavior; see issue #41. If the shell is POSIX, the whole expression with_redirections expr redirs exits and its return value is in [1, 125]; if the shell is "bash" or "zsh", the failing redirection is just ignored and expr is executed with the remaining redirections if any.

Redirect selected streams or the return value to files (stdout, stderr, return_value are paths).

write_stdout ~path expr is write_output expr ~stdout:path.

Pipe commands together ("stdout" into "stdin" exactly like the " | " operator).

a ||> b is a shortcut for pipe [a; b].

Get the contents of stdout into a byte array (in previous versions this function was called output_as_string).

Feed some content (~string) into the "stdin" filedescriptor of a unit t expression.

str >> cmd is feed ~string:str cmd.

printf fmt l is call (string "printf" :: string "--" :: fmt :: l).

Like printf but redirected to "stderr".

Expression that aborts the whole script/command immediately, it will try to output its argument to stderr (but this may be silent depending on the redirections active at a given time).

Abstraction of a file, cf. tmp_file.

Create a temporary file that may contain arbitrary strings (can be used as variable containing string t values).

tmp_file "foo" points to a path that is a function of the string "foo"; it does not try to make temporary-files unique, on the contrary: two calls to tmp_file "foo" ensure that it is the same file.

Typed command-line parsing for your shell scripts, à la Printf.scanf.

loop_until_true eval_condition tries to run eval_condition in a loop until it succeeds. It makes ~attempts attemps (default 20), and sleeps for sleep seconds (default 2) after each failed attempt. The argument ~on_failed_attempt can be used for instance to display something between each failed attempt and the call to sleep, the default is

fun nth -> printf (string "%d.") [Integer.to_string nth]

.

silently expr is expr with stdout and stderr redirected to "/dev/null".

succeeds_silently u is silently u |> succeeds.

seq_and [a; b; c] is like succeeds a &&& succeeds b &&& succeeds c.

output_markdown_code "ocaml" (exec ["echo"; "let x = 42"]) runs its second argument within markdown-like code fences.

cat_markdown tag path outputs the contents of the file at path (with "cat") within a markdown code bloc.

Run a sequence of expressions until the first that fails:

• ?verbosity configures the output behavior,

  • `Announce prompt uses prompt to output the name-tag of the command, the output of the command is redirected to temporary files (accessible through the ~on_success and ~on_failure functions). The default value is `Announce ">> ".
  • `Output_all lets all the output of the commands go through.
  • `Silent is like `Announce _ but without even the “prompt” command annoucement.
• ?on_failure configures what to do when encountering the first failure, the default is to display on stdout the name-tag of the failing command and outputting the contents of its stdout and stderr log-files (if any) and then call exec ["false"].
• ?on_success is a similar function as ?on_failure, called before starting the next command, the default is to do nothing.
• ?tmpdir configures where to create the logging files.

on_stdin_lines body builds a loop that iterates over the lines of the stdin file descriptor. The argument of `body` is the current line. Note that this is for text-like input, '\000' characters in the input lead to undefined behavior.

The Magic module is like OCaml's Obj.magic function for the EDSL; it allows one to bypass typing.