Popular Python recipes tagged "bash"

A utility like Unix seq (command-line), in Python (Python)

2017-01-08T17:48:57-08:00

Python recipe 580744 by Vasudev Ram (bash, command, commandline, linux, script, seq, sequence, shell, unix, utilities, utility).

This recipe shows how to create a utility like Unix seq (command-line), in Python. seq is described here:

https://en.wikipedia.org/wiki/Seq_(Unix)

but briefly, it is a command-line utility that takes 1 to 3 arguments (some being optional), the start, stop and step, and prints numbers from the start value to the stop value, on standard output. So seq has many uses in bigger commands or scripts; a common category of use is to quickly generate multiple filenames or other strings that contain numbers in them, for exhaustive testing, load testing or other purposes. A similar command called jot is found on some Unix systems.

This recipe does not try to be exactly the same in functionality as seq. It has some differences. However the core functionality of generating integer sequences is the same (but without steps other than 1 for the range).

More details and sample output are here:

https://jugad2.blogspot.in/2017/01/an-unix-seq-like-utility-in-python.html

The code is below.

Collection Pipeline in Python (Python)

2016-03-16T14:45:02-07:00

Python recipe 580625 by Steven D'Aprano (bash, filter, map, pipe, pipline).

A powerful functional programming technique is the use of pipelines of functions. If you have used shell scripting languages like bash, you will have used this technique. For instance, to count the number of files or directories, you might say: ls | wc -l. The output of the first command is piped into the input of the second, and the result returned.

We can set up a similar pipeline using Lisp-like Map, Filter and Reduce special functions. Unlike the standard Python map, filter and reduce, these are designed to operate in a pipeline, using the same | syntax used by bash and other shell scripting languages:

>>> data = range(1000)
>>> data | Filter(lambda n: 20 < n < 30) | Map(float) | List
[21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0]

The standard Python functional tools is much less attractive, as you have to write the functions in the opposite order to how they are applied to the data. This makes it harder to follow the logic of the expression.

>>> list(map(float, filter(lambda n: 20 < n < 30, data)))
[21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0]

We can also end the pipeline with a call to Reduce to collate the sequence into a single value. Here we take a string, extract all the digits, convert to ints, and multiply:

>>> from operator import mul
>>> "abcd12345xyz" | Filter(str.isdigit) | Map(int) | Reduce(mul)
120

A UNIX-like "which" command for Python (Python)

2015-03-20T19:23:45-07:00

Python recipe 579035 by Vasudev Ram (bash, commandline, commands, linux, shell, unix, utilities, which).

UNIX users are familiar with the which command. Given an argument called name, it checks the system PATH environment variable, to see whether that name exists (as a file) in any of the directories specified in the PATH. (The directories in the PATH are colon-separated on UNIX and semicolon-separated on Windows.)

This recipe shows how to write a minimal which command in Python. It has been tested on Windows.

Bash completed man and info pages generation (Python)

2011-08-24T03:14:13-07:00

Python recipe 577854 by Josh D (a, all, and, bash, be, command, completed, consume, file, first, generation, get, in, info, line, man, modify, must, only, pages, possibilties, possiblities, py, python, run, script, so, tab, terminal, the, this, to). Revision 6.

The script it self is very self explaining - the task is simple. *NIX only unless with cygwin perhaps?

To start this open a terminal and strike the "Tab" key to get all possibilities (strike y, and strike the space key alot). Select all then Copy and save in "comms.txt" Modify the file so ONLY the possiblities consume a line; no prompts or extra newlines. (first line must be a command, the last line must be a command)

Save the file ("~/Documents/bashing/comms.txt" is my path) then run this script in "~/Documents/bashing/".

This generates two (2) files: "bash_help_man.sh", "bash_help_info.sh".

Then it runs these files: "bash bash_help_man.sh", "bash bash_help_info.sh".

This produces 2 files for every command (every line) in "comms.txt". All manpages are wrote in "mans/", all infopages are wrote in "infos/"

There is now alot of files to read and organize; lets separate these by size. Directories are under1kb, under2kb, etc.

Once complete do as you wish the files less than 128 kb; these files are COPIED into there new respective home, I repeat COPIED.

The files 128 kb and higher ARE NOT copied to anywhere!

Line-oriented processing in Python from command line (like AWK) (Python)

2011-04-14T19:49:16-07:00

Python recipe 577656 by Artur Siekielski (awk, bash, python, shell).

A very simple but powerful shell script which enables writing ad-hoc Python scripts for processing line-oriented input. It executes the following code template:

$INIT
for line in sys.stdin:
    $LOOP
$END

where $INIT, $LOOP and $END code blocks are given from command line. If only one argument is given, then $INIT and $END are empty. If two arguments are given, $END is empty.

Examples (script is saved as 'pyk' in the $PATH):

"wc -l" replacement: $ cat file | pyk 'c=0' 'c+=1' 'print c'
grep replacement: $ cat file | pyk 'import re' 'if re.search("\d+", line): print line'
adding all numbers: $ seq 1 10 | pyk 's=0' 's+=int(line)' 'print s'
prepending lines with it's length: $ cat file | pyk 'print len(line), line'
longest file name: $ ls -1 | pyk 'longest=""' 'if len(line) > len(longest): longest=line' 'print longest'
number of unique words in a document: $ pyk 'words=[]' 'words.extend(line.split())' 'print "All words: {}, unique: {}".format(len(words), len(set(words))'

Better quote module for bash shells (Python)

2010-12-03T09:16:45-08:00

Python recipe 577483 by Kevin L. Sitze (bash, command, commandline, escape, logging, quote, script, shell).

This Python module quotes a Python string so that it will be treated as a single argument to commands ran via os.system() (assuming bash is the underlying shell). In other words, this module makes arbitrary strings "command line safe" (for bash command lines anyway, YMMV if you're using Windows or one of the (less fine) posix shells).