The Embedded Domain Specific Lanaguage to create “shell-expressions.”
type 'a t = 'a Language.t
The type of a Genspio expression.
type str = Language.byte_array
Type to encode arbitrary byte-arrays in the EDSL as
str t values, OCaml literal strings or the outputs (as in
stdout) of processes are byte-arrays.
NUL-terminated “C-like” strings are encoded at a lower level than this 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. Genspio treats them properly by failing when a wrong byte-array needs to be converted to a C-string.
type byte_array = Language.byte_array
type c_string = Language.c_string
val int : int -> int t
val bool : bool -> bool t
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.
Basic system Commands
Call a command from its list of “arguments” (including the first argument being the actual command).
val exec : string list -> unit t
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.
~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
Check whether a file exists, i.e. a shortcut for
call [str "test"; str "-f"; path] |> succeeds.
module Bool : sig ... end
Conversions of the
bool t type.
module Integer : sig ... end
int t values (arithmetic, comparisons, conversions, etc.).
module Elist : sig ... end
'a list t values.
module Str : sig ... end
val nop : unit t
The silent “no-operation.”
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
?e is provided) or
if_then (otherwise) that takes “then” and “else” bodies which are lists for the
Create a normal case for a
Redirections and File Descriptors
val to_fd : int t -> int t -> fd_redirection
Create a file-descriptor to file-descriptor redirection.
val to_file : int t -> str t -> fd_redirection
Create a file-descriptor to file redirection.
val with_redirections : unit t -> fd_redirection list -> unit t
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
"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 (
return_value are paths).
write_stdout ~path expr is
write_output expr ~stdout:path.
Pipe commands together (
"stdin" exactly like the
" | " operator).
Get the contents of
stdout into a byte array (in previous versions this function was called
Feed some content (
~string) into the
"stdin" filedescriptor of a
unit t expression.
printf fmt l is
call (string "printf" :: string "--" :: fmt :: l).
Escaping The Execution Flow
val fail : string -> unit t
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).
type file = < get : str t ; set : str t -> unit t ; append : str t -> unit t ; delete : unit t ; path : str t >
Abstraction of a file, cf.
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.
Command Line Parsing
module Command_line : sig ... end
Typed command-line parsing for your shell scripts, à la
Additional Higher-Level Utilities
val loop_until_true : ?attempts:int -> ?sleep:int -> ?on_failed_attempt:(int t -> unit t) -> bool t -> bool t
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
stderr redirected to
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
"cat") within a markdown code bloc.
val check_sequence : ?verbosity:[ `Announce of string | `Output_all | `Silent ] -> ?on_failure: (step:(string * unit t) -> stdout:str t -> stderr:str t -> unit t) -> ?on_success: (step:(string * unit t) -> stdout:str t -> stderr:str t -> unit t) -> ?tmpdir:string -> (string * unit t) list -> unit t
Run a sequence of expressions until the first that fails:
?verbosityconfigures the output behavior,
promptto output the name-tag of the command, the output of the command is redirected to temporary files (accessible through the
~on_failurefunctions). The default value is
`Announce ">> ".
`Output_alllets all the output of the commands go through.
`Announce _but without even the “prompt” command annoucement.
?on_failureconfigures 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
stderrlog-files (if any) and then call
?on_successis a similar function as
?on_failure, called before starting the next command, the default is to do nothing.
?tmpdirconfigures 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.
"command -v" to know if an executable is in
"$PATH" (note that
"which" is not POSIX, we use
"command -v ..." which is expected to return a failure if the command is not found).
Get the output of a command as a string without new lines, potentially cutting at the first line:
get_stdout ( (if first_line then u ||> exec ["head"; "-n"; "1"] else u) ||> exec ["tr"; "-d"; (if remove_spaces then " \\n" else "\\n")] )
call but print on
stderr the command being run.
A shortcut for
~verbosity:`Output_all hence ignoring the “names” of the commands.
val exit : int -> unit t
"exit ...", warning: depending on the compiler, the call maybe nested in various sub-shells, to really exit a script use
- Test the condition.
truedo nothing, succeed
- Test the condition again, if
Failures happen thanks to the !
Test a string or regular expression again the output of an expression.
“Smart pager” command to pipe long outputs through, conditions are tested in this order:
~disableis provided it can be used to make the pager behave like
- If the
str "1") is not a terminal, the command will be
- If the environment variable
"PAGER"it will be used as a shell command (
"sh -c ..").
- The last resort default is
~default_command(which by default value is
module Script_with_describe (P : sig ... end) : sig ... end
Make scripts that provide a
module Dispatcher_script : sig ... end
Create a script that mostly behaves like
"git", it concatenates its name with its first argument to call