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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.

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/’

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

ls -l | awk ‘{print $5, $NF}’ ls -l | pawk ‘f[4], f[-1]’

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 ‘print 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 pawk file and place it somewhere.

## 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

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.

## 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 |
pawk
–statement –begin ‘c=0’ –end ‘print c’ ‘c += os.stat(f[0]).st_size’

Short-flag version:

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

Transform /etc/hosts into a JSON map of host to IP:

cat /etc/hosts | pawk -sB ‘d={}’ -E ‘print json.dumps(d)’
‘if not l.startswith(“#”): d[f[1]] = f[0]’

### 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 README.md |
pawk
–statement –end ‘print markdown.markdown(t)’

Short-flag version:

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

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