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A Python line-processor (like awk) based on pyline.

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# PAWK - A Python line processor (like AWK)

PAWK aims to bring the full power of Python to AWK-like line-processing.

Here are some quick examples to show some of the advantages of pawk over AWK.

The first example transforms /etc/hosts into a JSON map of host to IP:

cat /etc/hosts | pawk -sB ‘d={}’ -E ‘json.dumps(d)’ ‘!/^#/ d[f[1]] = f[0]’

And another example showing how to bzip2-compress + base64-encode a file:

cat | pawk -sE ‘print base64.encodestring(bz2.compress(t))’

### AWK example translations

Most basic AWK constructs are available. You can find more idiomatic examples below in the example section, but here are a bunch of awk commands and their equivalent pawk commands to get started with:

Print lines matching a pattern:

ls -l / | awk ‘/etc/’ ls -l / | pawk ‘/etc/’

Print lines not matching a pattern:

ls -l / | awk ‘!/etc/’ ls -l / | pawk ‘!/etc/’

Field slicing and dicing (here pawk wins because of Python’s array slicing):

ls -l / | awk ‘/etc/ {print $5, $6, $7, $8, $9}’ ls -l / | pawk ‘/etc/ f[4:]’

Begin and end end actions (in this case, summing the sizes of all files):

ls -l | awk ‘BEGIN {c = 0} {c += $5} END {print c}’ ls -l | pawk -s -B ‘c = 0’ -E ‘c’ ‘c += int(f[4])’

Print files where a field matches a numeric expression (in this case where files are > 1024 bytes):

ls -l | awk ‘$5 > 1024’ ls -l | pawk ‘int(f[4]) > 1024’

Matching a single field (any filename with “t” in it):

ls -l | awk ‘$NF ~/t/’ ls -l | pawk ‘“t” in f[-1]’

## Installation

It should be as simple as:

` pip install pawk `

But if that doesn’t work, just download the, make it execuatable, and place it somewhere in your path.

## Expression evaluation

PAWK evaluates a Python expression (or statement if –statement is provided) against each line in stdin. The following variables are available in local context:

  • line - Current line text, including newline.
  • l - Current line text, excluding newline.
  • n - The current 1-based line number.
  • f - Fields of the line (split by the field separator -F).
  • nf - Number of fields in this line.
  • m - Tuple of match regular expression capture groups, if any.

Additionally, the –import <module>[,<module>,…] flag can be used to import symbols from a set of modules into the evaluation context.

eg. –import os.path will import all symbols from os.path, such as os.path.isfile(), into the context.

## Output

### Line actions

The type of the evaluated expression determines how output is displayed:

  • tuple or list: the elements are converted to strings and joined with the output delimiter (-O).
  • None or False: nothing is output for that line.
  • True: the original line is output.
  • Any other value is converted to a string.

### Start/end blocks

End and begin blocks are statements, but if the result of the statement is not None it will be displayed via repr(). This is a useful shortcut for non-string values, but strings will look like their Python representation:

$ echo -ne ‘foonbar’ | pawk -sE t ‘foonbar’

Explicitly print the output if this is not desirable:

$ echo -ne ‘foonbar’ | pawk -sE ‘print t’ foo bar

## Examples

### Line processing

Print the name and size of every file from stdin:

find . -type f | pawk ‘f[0], os.stat(f[0]).st_size’

> Note: this example also shows how pawk automatically imports referenced modules, in this case os.

Print the sum size of all files from stdin:

find . -type f |
–statement –begin ‘c=0’ –end c ‘c += os.stat(f[0]).st_size’

Short-flag version:

find . -type f | pawk -sB c=0 -E c ‘c += os.stat(f[0]).st_size’

### Whole-file processing

If statement mode (-s)is enabled and you do not provide a line expression, pawk will accumulate each line, and the entire file’s text will be available in the end statement as t. This is useful for operations on entire files, like the following example of converting a file from markdown to HTML:

cat |
–statement –end ‘print markdown.markdown(t)’

Short-flag version:

cat | pawk -sE ‘print markdown.markdown(t)’

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