pysh

Write shell scripts in Python

Basic

In pysh, lines that starts with > are executed as shell command. Other lines are evaluated as normal Python script.

for i in xrange(100):
   index = "%02d" % i
   > mv from$index.txt to$index.txt

For example, this pysh script moves from00.txt, from01.txt, …, from99.txt to to00.txt, to01.txt, …, to99.txt.

Pysh provides the following features

• You can use Python to write shell scripts!
• Lines with > prefix are executed as shell command.
• You can use Python variables and expressions in shell command.
• Most of useful shell features like pipe, redirection, &&, || and `cmd` are supported in pysh.
• You can implement flexible filter and conversion by using map and filter commands with Python lambda expression. You don't need to learn grep, awk and sed any longer.
• You can write built-in command by Python. Also, you can send Python object through pipe between built-in commands.

See Features section for details.

Install and run

git clone https://github.com/yunabe/pysh.git
./pysh/bin/pysh

pysh command

Run scripts from files

$ pysh script.pysh

Also, you can write pysh script by adding #!/path/to/pysh (or /usr/bin/env pysh) at the top of script files.

#!/path/to/pysh
# hello.sh
import os
> echo Hello ${os.getlogin()}

Run hello.sh

$ ./hello.sh
Hello yunabe

Run scripts from stdin

pysh - << 'EOF' arg0 arg1
import sys
> echo ${str(sys.argv[1:])}
EOF

This is useful when you write a oneliner in interactive shell like bash and zsh.

Run scripts from command line args

echo foo bar | pysh -c "`cat << 'EOF'
import sys
print repr(sys.stdin.read())
> echo ${str(sys.argv[1:])}
EOF`" arg0 arg1

This is useful when you define a shell function (e.g. in .bashrc) with pysh.

Features

Variable

In pysh, you can use python variable from shell scripts.

x = 3
y = x * x
> echo $y     # 9
> echo $PATH  # os.environment['PATH']

Python expression

In pysh, you can use any python expression by ${…}.

> echo ${3 + 4}  # 7
def f(x):
    return x * x
> echo ${f(10)}  # 100
> echo ${lambda x: x}

Pipe

Pipe is supported in pysh.

> echo "foo\nbar" | tac

Redirection

Redirection is also supported in pysh.

> echo "Hello world" > /dev/null
> echo "Hello world" >> /dev/null
> echo "Hello world" 2>&1

; && ||

> echo foo; echo bar
> echo foo && echo bar
> echo foo || echo bar

String literal

The format of string literal in pysh is equivalent with string literal in Python (In other words, it's different from other shells.) You can use escape characters like \n, \t. If you are familiar with Python, you don't need to learn another string literal format.

> echo "a\nb"

In pysh, variables ($i) and python expression (${…}) in string literals are evaluated if string literal is double-quoted. If string literal is single-quoted, pysh does not evaluate $i, ${…} in literals.

> echo "$i"
> echo '$i'

map, reduce, filter

map, reduce and filter builtin commands are available in pysh. These commands read data from pipe and apply "python" function in arg.

map

> seq 10 | map ${lambda s: int(s) * int(s)}
1
4
9
...

filter

> seq 10 | filter ${lambda s: int(s) % 3 == 0}
3
6
9

reduce

> seq 10 | reduce ${lambda x, y: int(x) + int(y)}
55

Multiline

Like other shell script, you can continue lines with backslash at the end of line.

> echo foo\
    bar

Store return code

You can store return code of programs with ->.

> (python -c 'import sys;sys.exit(2)' -> rc0\
    || python -c 'import sys;sys;exit(0)' -> rc1)
> print rc0, rc1  # 512 0

Redirect to Python

You can redirect output to Python variable with =>. The output is stored to Python variable as list (each line is stored as each element of a list).

> seq 5 | grep -v 3 => out
print out  # ['1', '2', '4', '5']
> send ${xrange(5)} | filter ${lambda i: i != 3} => out
print out  # [0, 1, 2, 4]

Backquote

You can use backquote to use results of commands as command arguments.

> echo `expr 3 + 4`  # 7

Python builtin command

You can write builtin commands in Python. See builtin.py for details.