FS(1) FS(1)
NAME
fs - file-hierarchy traversal
SYNOPSIS
fs verb arg
DESCRIPTION
Fs evaluates an expression whose values represent the con-
tents of a hierarchical filesystem. There are six types of
value:
fs The complete contents of a filesystem.
entries Information about the entries in a filesystem
without their content.
gate A condition that can be used with conditional
verbs. A gate is open to entries satisfying par-
ticular criteria.
selector A comparator which compares two entries and
selects one, both or neither of them.
string A simple string literal, represented by itself, or
quoted according to the usual shell quoting rules.
command A shell command, represented by an ``@'' character
followed by a braced block containing the shell
commands.
void 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 argu-
ments.
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:
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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 opera-
tors, useful when merging filesystems. Op speci-
fies the operator, taking its name from the graph-
ical Porter-Duff equivalent: AinB, AinB, BinA,
AoutB, BoutA, A, AoverB, AatopB, AxorB, B, BoverA,
or BatopA. For instance, AinB gives the intersec-
tion 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 - directo-
ries 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.
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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 com-
mand (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 environ-
ment 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 file-
name 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 regu-
lar expression, otherwise it is a shell-style pat-
tern 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
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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 path-
name 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 con-
tain any / characters).
size entries -> void
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FS(1) FS(1)
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 under-
neath 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 conver-
sions (conversions are applied recursively, so for instance,
an fs-valued expression at the top level will converted to
void by applying {print {entries fs}}.
string->fs
The result is {walk string}.
fs->entries
The result is {entries fs}.
string->gate
The result is {match string}.
entries->void
The result is {print entries}.
command->string
The result is {run command}.
EXAMPLES
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:
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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
SOURCE
/appl/cmd/fs.b
/appl/cmd/fs/*.b
/appl/lib/fslib.b
SEE ALSO
sh(1)
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