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A shell power-up for working with the file system and running subprocess commands.


  • Run and define subprocess commands

    • run

    • cmd

  • Interact with files

    • atomicdfile, atomicdir

    • read, readchunks, readlines, readtext, readbytes

    • write, writechunks, writelines, writetext, writebytes

    • fsync, dirsync

  • Execute core shell operations

    • cp, mv, mkdir, touch

    • rm, rmfile, rmdir

    • ls, lsfiles, lsdirs

    • walk, walkfiles, walkdirs

  • Archive and backup files

    • archive, unarchive, lsarchive

    • backup

  • Other utilities

    • cd

    • environ

    • cwd, homedir

    • and more!

  • 100% test coverage

  • Fully type-annotated

  • Python 3.6+


Install using pip:

pip3 install shelmet

Import the sh module:

import shelmet as sh

Run system commands:

# is a wrapper around that defaults to output capture, text-mode,
# exception raising on non-zero exit codes, environment variable extension instead of
# replacement, and support for passing command arguments as a variable number of strings
# instead of just a list of strings.
result ="ps", "aux")

# stdout and stderr can be combined with...
result ="some", "command", combine_output=True)

# or not captured at all..."...", capture_output=False)

Create reusable run commands that support chained commands like “pipe” | , “and” &&, “or” ||, and “after” ;:

# sh.cmd() returns a sh.Command object that can be used to execute a fixed command.
ps_aux = sh.cmd("ps", "aux")

# And has the option to pipe it's output into another command automatically.
grep_ps = ps_aux.pipe("grep", "-i", check=False)
# ps aux | grep -i

search_result_1 ="search term 1")

search_result_2 ="search term 2")

# Equivalent to: mkdir foo && echo 'success' || echo 'failure'
sh.cmd("mkdir", "foo").and_("echo", "success").or_("echo", "failure").run()

Perform file system operations:

# Make directories and sub-directories. Behaves like "$ mkdir -p"
sh.mkdir("a", "b", "c", "d/e/f/g")

# Context-manager to change working directory temporarily. Behaves like "$ cd".
    sh.touch("1.txt", "2.txt", "3.txt")

    # Move files or directories. Works across file-systems. Behaves like "$ mv"."1.txt", "11.txt")

    # Copy files or directories. Behaves like "$ cp -r"
    sh.cp("2.txt", "22.txt")

    # List top-level directory contents.
    # NOTE: and its siblings return iterables.

    # Limit to files.

    # Limit to directories.

    # Remove files.
    sh.rmfile("11.txt", "22.txt", "3.txt")
    # Or use sh.rm which handles both files and directories.
    sh.rm("11.txt", "22.txt", "3.txt")

# Recursively walk current directory.
# NOTE: sh.walk() and its siblings return iterables.

# Or just a specified directory.

# Or just it's files or directories.

# Remove directories.
sh.rmdir("a", "b", "c", "d")
# Or use sh.rm which handles both files and directories.
sh.rm("a", "b", "c", "d")

Perform file IO:

sh.write("test.txt", "some text\n")
sh.write("test.txt", " some more text\n", "a")

sh.write("test.bin", b"some bytes")
sh.write("test.bin", b" some more bytes", "ab")

sh.writelines("output.txt", ["1", "2", "3"])              # -> "1\n2\n3\n"
sh.writelines("output.txt", (str(i) for i in range(5)))  # -> "0\n1\n2\n3\n4\n"

# Write to a file atomically. See sh.atomicfile for more details.
sh.write("test.txt", "content", atomic=True)
sh.writelines("test.txt", ["content"], atomic=True)

text ="test.txt")        # -> "some text\nsome more text\n"
data ="text.bin", "rb")  # -> b"some bytes some more bytes"

for line in sh.readlines("test.txt"):

for chunk in sh.readchunks("test.txt", size=1024):

sh.write("test.txt", "a|b|c|d")
items = list(sh.readchunks("test.txt", sep="|"))
print(items)  # -> ["a", "b", "c", "d"]

sh.write("test.txt", b"a|b|c|d", "wb")
assert "".join(sh.readchunks("test.txt", "rb", sep=b"|")) == b"a|b|c|d"

Backup files:

# Create backup as copy of file.
backup_file = sh.backup("a.txt")
print(backup_file)                                  # a.txt.2021-02-24T16:19:20.276491~
sh.backup("a.txt", utc=True)                        # a.txt.2021-02-24T11:19:20.276491Z~
sh.backup("a.txt", epoch=True)                      # a.txt.1614878783.56201
sh.backup("a.txt", suffix=".bak")                   # a.txt.2021-02-24T16:19:20.276491.bak
sh.backup("a.txt", suffix=".bak", timestamp=False)  # a.txt.bak
sh.backup("a.txt", prefix="BACKUP_", suffix="")     # BACKUP_a.txt.2021-02-24T16:19:20.276491

# Create backup as copy of directory.
sh.backup("path/to/dir")                            # path/to/dir.2021-02-24T16:19:20.276491~

# Create backup as archive of file or directory.
sh.backup("b/c", ext=".tar.gz")                    # b/c.2021-02-24T16:19:20.276491.tar.gz
sh.backup("b/c", ext=".tar.bz2")                   # b/c.2021-02-24T16:19:20.276491.tar.bz2
sh.backup("b/c", ext=".tar.xz")                    # b/c.2021-02-24T16:19:20.276491.tar.xz
sh.backup("b/c", ext=".zip")                       # b/

from functools import partial
import itertools

counter = itertools.count(1)
backup = partial(sh.backup, namer=lambda src: f"{}-{next(counter)}~")
backup("test.txt")  # test.txt-1~
backup("test.txt")  # test.txt-2~
backup("test.txt")  # test.txt-3~

Archive files:

# Create tar, tar-gz, tar-bz2, tar-xz, or zip archives.
sh.archive("archive.tar.gz", "/path/to/foo", "/path/to/bar")

# Archive type is inferred from extension in filename but can be explicitly set.
sh.archive("archive", "path", ext=".tbz")

# Files can be filtered with ls, lsfiles, lsdirs, walk, walkfiles, and walkdirs functions.
    sh.walk("path", include="*.py"),
     sh.walk("other/path", exclude="*.log"),

# Archive paths can be customized with root and repath arguments.
# root changes the base path for archive members.
sh.archive("archive.txz", "/a/b/c/1", "/a/b/d/2", root="/a/b")
# -> archive members will be "c/1/*" and "d/2/*"
# -> without root, they would be "b/c/1/*" and "b/d/2/*"

# repath renames paths.
sh.archive("", "/a/b/c", "/a/b/d", repath={"/a/b/c": "foo/bar"})
# -> archive members: "foo/bar/*" and "b/d/*"

# repath also works with ls* and walk* by matching on the base path.
    sh.walk("path/to/logs", include="*.log*"),
    repath={"path/to/logs": "logs"},

Get list of archive contents:

# Get list of archive contents as PurePath objects.
listing = sh.lsarchive("archive.tgz")

# Use an explicit extension when archive doesn't have one but is supported.
listing = sh.lsarchive("archive", ext=".tgz")

Unarchive tar and zip based archives:

# Extract tar, tar-gz, tar-bz2, tar-xz, or zip archives to directory.
sh.unarchive("archive.tgz", "out/dir")

# Potentially unsafe archives will raise an exception if the extraction path falls outside
# the destination, e.g., when the archive contains absolute paths.
    sh.unarchive("unsafe-archive.tz2", "out")
except sh.ArchiveError:

# But if an archive can be trusted...
sh.unarchive("unsafe-archive.tz2", "out")

Write to a new file atomically where content is written to a temporary file and then moved once finished:

import os

with sh.atomicfile("path/to/atomic.txt") as fp:
    # Writes are sent to a temporary file in the same directory as the destination.
    print( # will be something like "path/to/.atomic.txt_XZKVqrlk.tmp"
    fp.write("some text")
    fp.write("some more text")

    # File doesn't exist yet.
    assert not os.path.exists("path/to/atomic.txt")

# Exiting context manager will result in the temporary file being atomically moved to
# destination. This will also result in a lower-level fsync on the destination file and
# directory.
assert os.path.exists("path/to/atomic.txt")

# File mode, sync skipping, and overwrite flag can be specified to change the default
# behavior which is...
with sh.atomicfile("file.txt", "w", skip_sync=False, overwrite=True) as fp:

# Additional parameters to open() can be passed as keyword arguments.
with sh.atomicfile("file.txt", "w", **open_kwargs) as fp:

# To writie to a file atomically without a context manager
sh.write("file.txt", "content", atomic=True)

Create a new directory atomically where its contents are written to a temporary directory and then moved once finished:

with sh.atomicdir("path/to/atomic_dir") as atomic_dir:
    # Yielded path is temporary directory within the same parent directory as the destination.
    # path will be something like "path/to/.atomic_dir_QGLDfPwz_tmp"
    some_file = atomic_dir / "file.txt"

    # file written to "path/to/.atomic_dir_QGLDfPwz_tmp/file.txt"

    some_dir = atomic_dir / "dir"
    some_dir.mkdir()  # directory created at "path/to/.atomic_dir_QGLDfPwz_tmp/dir/"

    # Directory doesn't exist yet.
    assert not os.path.exists("path/to/atomic_dir")

# Exiting context manager will atomically move the the temporary directory to the destination.
assert os.path.exists("path/to/atomic_dir")

# Sync skipping and overwrite flag can be specified to change the default behavior which is...
with sh.atomicdir("atomic_dir", skip_sync=False, overwrite=True) as atomic_dir:

Temporarily change environment variables:

# Extend existing environment.
with sh.environ({"KEY1": "val1", "KEY2": "val2"}) as new_environ:
    # Do something while environment changed.
    # Environment variables include all previous ones and {"KEY1": "val1", "KEY2": "val2"}.

# Replace the entire environment with a new one.
with sh.environ({"KEY": "val"}, replace=True):
    # Environment variables are replaced and are now just {"KEY": "val"}.

For more details, please see the full documentation at


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