[manual index][section index]


fs - file-hierarchy traversal


fs verb arg


Fs evaluates an expression whose values represent the contents of a hierarchical filesystem. There are six types of value:

The complete contents of a filesystem.
Information about the entries in a filesystem without their content.
A condition that can be used with conditional verbs. A gate is open to entries satisfying particular criteria.
A comparator which compares two entries and selects one, both or neither of them.
A simple string literal, represented by itself, or quoted according to the usual shell quoting rules.
A shell command, represented by an ``@'' character followed by a braced block containing the shell commands.
No value. An expression of this type cannot be used as an argument to any verb.

A value is represented either by a literal (a string or shell command), or by a braced block, {verb [arg...]}, whose value is the result of evaluating verb with the given arguments.

In the following description of the verbs provided, an entry such as:

print entries -> void

describes a verb print, which takes one argument of type entries, and the result of which is of type void. If the type is not one of those described above, it should be taken to be of type string.

With no arguments, fs prints a summary of the available verbs. Verbs understood by fs include:

and gate gate [gate...] -> gate
And is a gate that is open to an entry if all its arguments are open.
bundle fs -> void
Bundle converts fs to an archival format and writes it to the standard output.
compose [-d] op -> selector
Compose implements ``compositing''-style operators, useful when merging filesystems. Op specifies the operator, taking its name from the graphical Porter-Duff equivalent: AinB, AinB, BinA, AoutB, BoutA, A, AoverB, AatopB, AxorB, B, BoverA, or BatopA. For instance, AinB gives the intersection of A and B; AatopB gives A whereever both A and B exist, and B otherwise. When used as a selector for merge, operators that exclude the union of A and B are not very useful, as they will exclude all common directories at the top level. Given the -d option, compose will allow through directories that would otherwise be excluded in this way, making operators such as AxorB (all that A does not hold in common with B) more useful, although accurate only for regular files.
depth n -> gate
Depth is a gate open only to entries which are within n levels of the root of the filesystem.
entries fs -> entries
Entries produces all the entries contained within fs.
eval expr -> any
Eval evaluates an fs expression and yields its result.
filter [-d]gate fs -> fs
The result of filter is a filesystem from which all entries that will not pass through gate, and their descendents, have been removed. If the -d flag is given, only files are filtered - directories bypass the gate.
ls [-um] entries -> void
Print each entry in the style of ls -l (see ls(1)). If the -u flag is given, the file access time rather than the file modification time will be printed. If the -m flag is given, the name of the user that last modified the file is printed too.
exec [-pP] [-t command] [-n n] command entries -> void
Run its argument command for each entry in entries . If the -n flag is specified, exec will try to gather n entries together before invoking the command (default 1). The environent variable $file is set to the names of the entries that have been gathered. If the -p flag is given, environment variables are set giving information about the mode, owner, modification time and size of the entry (they are named after the equivalent field names in the Dir structure; see sys-stat(2)). This option is only valid when n is 1. The -P flag causes all the other fields in the Dir structure to be included too. Note that the command is run in the same shell context each time, so environment variable set on one execution can be retrieved on the next. The -t flag can be used to specify a command which will be executed just before termination.
match [-ar] pattern -> gate
Match is a gate that is open if the entry's filename matches the pattern. If the -a flag is given, the whole path will be used for the match. If -r is specified, the pattern is evaluated as a regular expression, otherwise it is a shell-style pattern in the style of filepat(2).
merge [-1] [-c selector] fs fs [fs...] -> fs
Recursively merge the contents of its argument filesystems. Selector is consulted to see which entries are chosen for the result; if not given, entries are resolved in favour of the first filesystem (equivalent to {compose AoverB}). If the -1 flag is given, merging takes place only in the top-level directory.
mode spec -> gate
Mode is a gate that lets through entries whose file permissions satisfy spec, which is a string in the style of chmod(1). If the op field is +, the specified permissions must be present; if -, they must be absent, and if =, they must be exactly as given. The directory and auth modes are specified with the characters ``d'' and ``A'' respectively.
not gate -> gate
Not is a gate open to an entry if its argument is not.
or gate gate [gate...] -> gate
Or is a gate open to an entry if any argument is open.
path [-x] path... -> gate
Path is a gate open to an entry whose full pathname is an ancestor or a descendent of any path. If -x is specified, the gate is open to any path except descendents of the paths given.
pipe [-1pP] command fs -> void
Pipe is similar to exec, except that the contents of all files in fs are piped through command. Unless the -1 option is given, command is started once for each file, with $file set to its name, and other environment variables set according to the -p or -P options, as for exec. If the -1 option is specified, command is started once only - all file data is piped through that.
print entries -> void
Print the path name of each entry.
proto [-r root] protofile -> fs
Evaluate protofile as a mkfs(8) proto file. If root is specified, it will be used as the root of the resulting fs.
query command -> gate
Query is a gate that runs command to determine whether it is open: an empty exit status from the command yields an open gate. The environment variable $file is set for the command to the path name of the entry that is being queried for.
run command -> string
Run runs command and substitutes the value of the environment variable $s after its invocation. $s must have exactly one element.
select gate entries -> entries
Select only those entries within entries that will pass through gate. Descendents of elided entries are not affected.
setroot [-c] path fs -> fs
Setroot sets the name of the root directory of fs. If the -c flag is given, the elements in the root directory will be made explicit in the hierarchy (i.e. the name of the top directory will not contain any / characters).
size entries -> void
Print the sum of the size of all entries, in bytes.
unbundle file -> fs
Unbundle reads an archive as produced by bundle from file; its result is the contents of the filesystem that was originally bundled. If file is ``-'', the standard input is read.
walk path -> fs
Walk produces a filesystem that's the result of traversing all the files and directories underneath path.
write dir fs -> void
Write the contents of fs to the filesystem rooted at dir . If dir is empty, fs will be written to the root directory originally associated with fs.

As a convenience, fs carries out some automatic type conversions (conversions are applied recursively, so for instance, an fs-valued expression at the top level will converted to void by applying {print {entries fs}}.

The result is {walk string}.
The result is {entries fs}.
The result is {match string}.
The result is {print entries}.
The result is {run command}.


Print the size of all files below the current directory:
	fs size .
Show the names of all files in x that aren't in y:
	fs select {mode -d} {merge -c {compose -d AoutB} x y}
Remove all files from /appl ending in .dis:
	fs exec @{rm $file} {select *.dis /appl}
Recursively copy the current directory to /tmp/foo.
	fs bundle . | fs write /tmp/foo {unbundle -}
A simpler method of the above:
	fs write /tmp/foo .
Interactively remove all regular files from one level of the current directory:

fs exec @{rm $file} {select {query
	@{echo -n $file:; ~ `{read} y yes}}
	{select {mode -d} {filter {depth 1} .}}}

Create a new archive containing those files from below the current directory that were held in an old archive:

	fs bundle {merge -c {compose AinB} . {unbundle old.bundle}} > new.bundle





FS(1 ) Rev:  Tue Mar 31 02:42:38 GMT 2015