Package: shlib
Author:Ken KundertVersion:1.6Released:2023-05-18A light-weight package with few dependencies that allows users to do
shell-script like things relatively easily in Python. Is a natural complement to
the pathlib library. Pathlib does pretty much what you would like to do with
a single path; shlib does similar things with many paths at once. For example,
with pathlib you can remove (unlink) a single file, but with shlib you can
remove many files at once. Furthermore, most of the features of pathlib are
implemented as pathlib methods, so you must convert your strings to paths before
you can use them. ShLib is equally comfortable with strings as with paths.Writing programs that substantially interact with the file system can be
surprisingly painful in Python because the code that is used to do so is spread
over many packages and those packages are not very compatible with each other
nor do they follow the conventions of the corresponding shell commands.This package, shlib, attempts to address those issues by providing one package
that combines the commonly used utilities for interacting with the filesystem
that follows the conventions used by the corresponding shell commands.It consists of replacements for some very common Unix utilities that interact
with the filesystem, such as cp, mv, rm, ln, mkdir, and cd. These tend to be
less fussy than their command line counter parts. For example, rm deletes both
files and directories without distinction and will not complain if the file or
directory does not exist. Similarly mkdir will create any child directories
needed and will not complain if the directory already exists.Finally, it provides several ways to run external programs.Each feature is designed to allow you to express your desires simply and
efficiently without worrying too much about exceptions.Most of the functions in this package take paths to files or directories. Those
paths may be specified either as strings or pathlib paths. Many of the functions
accept multiple paths, and those can be specified either as an array or as
individual arguments. Several of the functions return either a path or
a collection of paths. These paths are returned as pathlib paths.InstallationUse ‘pip3 install shlib’ to install. Requires Python3.6 or better.System Utility FunctionsCopy (cp)Copy files or directories:cp(src, ..., dest)or:cp([src, ...], dest)Copy all source items, whether they be files or directories to dest. If there is
more than one src item, then dest must be a directory and the copies will be
placed in that directory.  The src arguments may be strings, pathlib paths, or
collections of strings and paths.  The dest must be a string or path.Example:>>>fromshlibimport*>>>testdir='testdir'>>>rm(testdir)>>>mkdir(testdir)>>>files=cartesian_product(testdir,['f1','f2'])>>>touch(files)>>>dirs=cartesian_product(testdir,['d1','d2'])>>>mkdir(dirs)>>>print(sorted(str(e)foreinls(testdir)))['testdir/d1','testdir/d2','testdir/f1','testdir/f2']>>>cp('testdir/f1','testdir/f4')>>>print(sorted(str(f)forfinlsf(testdir)))['testdir/f1','testdir/f2','testdir/f4']>>>dest1=to_path(testdir,'dest1')>>>mkdir(dest1)>>>cp(files,dest1)>>>print(sorted(str(f)forfinlsf(dest1)))['testdir/dest1/f1','testdir/dest1/f2']>>>cp(dirs,dest1)>>>print(sorted(str(d)fordinlsd(dest1)))['testdir/dest1/d1','testdir/dest1/d2']>>>f1,f2=tuple(files)>>>dest2=to_path(testdir,'dest2')>>>mkdir(dest2)>>>cp(f1,f2,dest2)>>>print(sorted(str(f)forfinlsf(dest2)))['testdir/dest2/f1','testdir/dest2/f2']>>>dest3=to_path(testdir,'dest3')>>>mkdir(dest3)>>>cp([f1,f2],dest3)>>>print(sorted(str(f)forfinlsf(dest3)))['testdir/dest3/f1','testdir/dest3/f2']Move (mv)Move files or directories:mv(src, ..., dest)Move all source items, whether they be files or directories to dest. If there is
more than one src item, then dest must be a directory and everything will be
placed in that directory.  The src arguments may be strings or lists of strings.
The dest must be a string.>>>fromshlibimport*>>>testdir='testdir'>>>rm(testdir)>>>mkdir(testdir)>>>files=cartesian_product(testdir,['f1','f2'])>>>touch(files)>>>dirs=cartesian_product(testdir,['d1','d2'])>>>mkdir(dirs)>>>print(sorted(str(e)foreinls(testdir)))['testdir/d1','testdir/d2','testdir/f1','testdir/f2']>>>dest=to_path(testdir,'dest')>>>mkdir(dest)>>>mv(files,dest)# move a list of files>>>print(sorted(str(f)forfinlsf(dest)))['testdir/dest/f1','testdir/dest/f2']>>>mv(dirs,dest)# move a list of directories>>>print(sorted(str(d)fordinlsd(dest)))['testdir/dest/d1','testdir/dest/d2']Remove (rm)Remove files or directories:rm(path, ...)Delete all files and directories given as arguments. Does not complain if any of
the items do not exist.  Each argument must be either a string or a list of
strings.>>>print(sorted(str(e)foreinls(testdir)))['testdir/dest']>>>print(sorted(str(e)foreinls(dest)))['testdir/dest/d1','testdir/dest/d2','testdir/dest/f1','testdir/dest/f2']>>>rm(lsf(dest))>>>print(sorted(str(e)foreinls(dest)))['testdir/dest/d1','testdir/dest/d2']>>>rm(dest)>>>print(sorted(str(e)foreinls(testdir)))[]>>>rm(testdir)Link (ln)Create a symbolic link:ln(src, link)Creates a symbolic linklinkthat points tosrc.  Each argument must be
either a string.Make File (touch)Create a new empty file or update the timestamp on an existing file:touch(path, ...)Each argument must be either a string or a list of strings.Make Directory (mkdir)Create an empty directory:mkdir(path, ...)For each argument it creates a directory and any needed parent directories.
Returns without complaint if the directory already exists. Each argument must be
either a string or a list of strings.Change Directory (cd)Change to an existing directory:cd(path)Makes path the current working directory.May also be used in awithblock:with cd(path):
    cwd()The working directory returns to its original value upon leaving thewithblock.Current Working Directory (cwd)Returns the current working directory:path = cwd()Mount and Unmount a Filesystem (mount)Mount a filesystem with:mount(path)Then unmount it with:umount(path)You can test to determine if a filesystem is mounted with:is_mounted(path)May also be used in awithblock:with mount(path):
    cp(path/data, '.')The filesystem is unmounted upon leaving thewithblock.List Directory (ls, lsd, lsf)List a directory:ls(path, ... [<kwargs>])
lsd(path, ... [<kwargs>])
lsf(path, ... [<kwargs>])The first form returns a list of all items found in a directory. The second
returns only the directories, and the third returns only the files.One or more paths may be specified using unnamed arguments. The paths may be
strings or pathlib paths, or collections of those.  If no paths are not given,
the current working directory is assumed.The remaining arguments must be specified as keyword arguments.select=<glob-str>Ifselectis specified, an item is returned only if it matches the given
pattern.  Using ‘**’ inselectenables a recursive walk through a directory
and all its subdirectories.  Using ‘**’ alone returns only directories whereas
‘**/*’ returns files and directories.reject=<glob-str>Ifrejectis specified, an item is not returned if it matches the given
pattern.only={'file','dir'}Ifonlyis specified, it may be either ‘file’ or ‘dir’, in which case only
items of the corresponding type are returned.hidden=<bool>The value of hidden is a boolean that indicates whether items that begin with
‘.’ are included in the output. If hidden is not specified, hidden items are not
included unlessselectbegins with ‘.’.Examples:pyfiles = lsf(select='*.py')
subdirs = lsd()
tmp_mutt = lsf('/tmp/', select='mutt-*')File PermissionsChange the file permissiongs of a file, or files, or directory, or directories:chmod(mode, path)wheremodeis a three digit octal number.You may read the permissions of a file or directory using:mode = getmod(path)Pathsto_pathCreate a path from a collection of path segments:p = to_path(seg, ...)The segments are combined to form a path. Expands a leading ~. Returns a pathlib
path. It is generally not necessary to apply to_path() to paths being given to
the shlib functions, but using it gives you access to all of the various pathlib
methods for the path.>>>path=to_path('A','b','3')>>>str(path)'A/b/3'to_pathreturns a Path object that has been extended from the standard Python
pathlib Path object.  Specifically, it includes the following methods:p.is_readable()   — return True if path exists and is readable
p.is_writable()   — return True if path exists and is writable
p.is_executable() — return True if path exists and is executable
p.is_hidden()     — return True if path exists and is hidden (name starts with .)
p.is_newer()      — return True if path exists and is newer than argument
p.path_from()     — differs from relative_to() in that returned path will not start with ..
p.sans_ext()      — return full path without the extensionSeeextended_pathlibfor
more information.LeavesRecursively descend into a directory yielding paths to all of the files it
contains. Normally hidden files are excluded unless thehiddenargument is
True.  OSErrors found during the scan are ignored unless thereportargument
is specified, and if specified it must be a function that takes one argument,
the exception raised by the error.Cartesian ProductCreate a list of paths by combining from path segments in all combinations:cartesian_product(seg, ...)Like with to_path(), the components are combined to form a path, but in this
case each component may be a list. The results is the various components are
combined in a Cartesian product to form a list. For example:>>>paths=cartesian_product(['A','B'],['a','b'],['1','2'])>>>forpinpaths:...print(p)A/a/1A/a/2A/b/1A/b/2B/a/1B/a/2B/b/1B/b/2Brace ExpandCreate a list of paths using Bash-like brace expansion:brace_expand(pattern)>>>paths=brace_expand('python{2.{5..7},3.{2..6}}')>>>forpinsorted(str(p)forpinpaths):...print(p)python2.5python2.6python2.7python3.2python3.3python3.4python3.5python3.6Executing ProgramsThe following classes and functions are used to execute external programs from
within Python.Command (Cmd)A class that runs an external program:Cmd(cmd[, modes][, env][, encoding][, log][, option_args])cmdmay be a list or a string.modeis a string that specifies various options. The options are specified
using a single letter, with upper case enabling the option and lower case
disabling it:S, s: Use, or do not use, a shellO, o: Capture, or do not capture, stdoutE, e: Capture, or do not capture, stderrM, m: Merge, or do not merge, stderr into stdout (M overrides E, e)W, w: Wait, or do not wait, for command to terminate before proceedingIf a letter corresponding to a particular option is not specified, the default
is used for that option.  In addition, one of the following may be given, and it
must be given last*: accept any output status codeN: accept any output status code equal to or less than NM,N,…: accept status codes M, N, …If you do not specify the status code behavior, only 0 is accepted as normal
termination, all other codes will be treated as errors.  An exception is raised
if exit status is not acceptable. By default anOSErroris raised, however if
theuse_informpreference is true, theninform.Erroris used. In this case
the error includes attributes that can be used to access thestdout,stderr,status,cmd, andmsg.envis a dictionary of environment variable and their values.encodingis used on the input and output streams when converting them to and
from strings.logspecifies whether details about the command should be sent to log file.
May be True, False, or None. If None, then behavior is set bylog_cmdpreference. Use oflogrequires thatInformpackage be installed.option_argsis used when rendering command to logfile, it indicates how many
arguments each option takes.  This only occurs whenuse_informpreference is
true andInformpackage is installed.For example, to run diff you might use:>>> import sys, textwrap
>>> ref = textwrap.dedent('''
...     line1
...     line2
...     line3
... ''').strip()
>>> test = textwrap.dedent('''
...     line1
...     line2
... ''').strip()

>>> ref_bytes_written = to_path('./REF').write_text(ref)
>>> test_bytes_written = to_path('./TEST').write_text(test)

>>> cat = Cmd(['cat', 'TEST'], 'sOeW')
>>> cat.run()
0

>>> print(cat.stdout)
line1
line2

>>> diff = Cmd('diff TEST REF', 'sOEW1')
>>> status = diff.run()
>>> status
1Use ofOin the modes allows access to stdout, which is needed to access the
differences. SpecifyingEalso allows access to stderr, which in this case is
helpful in case something goes wrong because it allows the error handler to
access the error message generated by diff. SpecifyingWindicates that run()
should block until diff completes. This is also necessary for you to be able to
capture either stdout or stderr.  Specifying 1 indicates that either 0 or 1 are
valid output status codes; any other code output by diff would be treated as an
error.If you do not indicate that stdout or stderr should be captured, those streams
remain connected to your TTY. You can specify a string to the run() method,
which is fed to the program through stdin. If you don’t specify anything the
stdin stream for the program also remains connected to the TTY.If you indicate that run() should return immediately without out waiting for the
program to exit, then you can use the wait() and kill() methods to manage the
execution. For example:diff = Cmd(['gvim', '-d', lfile, rfile], 'w')
diff.run()
try:
    status = diff.wait()
except KeyboardInterrupt:
    diff.kill()Casting the object to a string returns the command itself:>>> print(str(cat))
cat TESTIf you call run(), then you should either specify ‘W’ as the wait mode, or you
should call the wait() method. If you do not, then any string you specified as
stdin is not applied. If your intention is to kick off a process and not wait
for it to finish, you should use start() instead. It also allows you to specify
a string to pass to stdin, however you cannot access stdout, stderr, or the exit
status. If you specify the ‘O’ or ‘E’ modes when using start(), those outputs
are simply discarded. This is a useful way of discarding uninteresting
diagnostics from the program you are calling.Cmdalso provides therendermethod, which converts the command to a string.
It takes the same optional arguments as doesrender_command.RunRunsubclassesCmd. It basically constructs the process and then immediately
calls the run() method. It takes the same arguments as Cmd, but an additional
argument that allows you to specify stdin for the process:Run(cmd[, modes][, stdin][, env][, encoding])Run expect you to wait for the process to end, either by specify the ‘W’ mode,
or by calling wait().  For example:>>> echo = Run('cat > helloworld', 'SoeW', 'hello world')
>>> echo.status
0

>>> echo = Run(['echo', 'helloworld'], 'sOew')
>>> echo.wait()
0

>>> print(echo.stdout.strip())
helloworldStartStart also subclasses Cmd. It is similar to Run in that it immediately executes
the command, but it differs in that it does not expect you to wait for the
command to terminate. You may specify stdin to the command if you wish, but
since you are not waiting for the command to terminate you cannot access stdout,
stderr or the exit status.  Effectively, Start() kicks off the process and then
ignores it.  You may pass wait or accept in the mode string, but they are
ignored. If you select either stdout or stderr to be captured, then are wired to
/dev/null, meaning that the selected output is swallowed and discarded.>>> cat = Start('cat helloworld', 'sOe')whichGiven a name, a path, and a collection of read, write, or execute flags, this
function returns the locations along the path where a file or directory can be
found with matching flags:which(name, path=None, flags=os.X_OK)By default the path is specified by the PATH environment variable and the flags
check whether you have execute permission.render_commandRender a command to a string:render_command(cmd[, option_args][, width])Converts the command to a string.  The formatting is such that you should be
able to feed the result directly to a shell and have command execute properly.cmdis the command to render. It may be a string or a list of strings.option_argsis a dictionary.  The keys are options accepted by the command and
the value is the number of arguments for that option.  If an option is not
found, it is assumed to have 0 arguments.widthspecifies how long the string must be before it is broken into multiple
lines.  If length of resulting line would be width or less, return as a
single line, otherwise place each argument and option on separate line.If the command is rendered as multiple lines, each argument and option is placed
on a separate line, while keeping argument to options on the same line as the
option.  Placing each option and argument on its own line allows complicated
commands with long arguments to be displayed cleanly.For example:>>> args = {'--dux': 2, '-d': 2, '--tux': 1}
>>> print(render_command('bux --dux a b -d c d --tux e f g h', args))
bux --dux a b -d c d --tux e f g h

>>> print(render_command('bux --dux a b -d c d --tux e f g h', args, width=0))
bux \
    --dux a b \
    -d c d \
    --tux e \
    f \
    g \
    hset_prefsUsed to set preferences that affect theCmdclass. The preferences are given
as keyword arguments.use_informindicates that theInformexceptionErrorshould be raised if
the exit status from a command is not acceptable. If this not given or is False,
an OSError is raised instead.  Use of this preference requires thatInformbe
available.  Ifuse_informis True, then inform.Error() is used byCmdand
its subclasses (RunandStart).log_cmdspecifies that the command and its exit status should be written to
theInformlog file.  Use of this preference requires thatInformbe
available.Error Reporting with InformTheCmdclass and its subclasses (RunandStart) raise anInformError if theuse_informpreference was
specified. This allows for rich error reporting. In particular, the command,
exit status, stdout and stderr are all returned with the exception and are
available to insert into an error message. For example:>> from shlib import Run, set_prefs
>> from inform import Error

>> set_prefs(use_inform=True)

>> try:
..     c = Run('sort words', 'sOEW0')
.. except Error as e:
..     e.report(template=(
..         '"{cmd}" exits with status {status}.\n    {stderr}',
..         '"{cmd}" exits with status {status}.',
..     ))
error: "sort words" exits with status 2.
    sort: cannot read: words: No such file or directory.If command returns a non-zero exit status, an exception is raised and one of two
error messages are printed. The first is printed ifstderris not empty, and
the second is printed if it is.Most other functions raise an OSError upon an error.  You can useInformto
convert this exception into a reasonable error message:>> from inform import fatal, os_error
>>
>> try:
..    cp(from, to)
.. except OSError as e:
..    fatal(os_error(e))