bash-filter

This script provides the missing filter functionality for bash.

Installation

Checkout the source code:

$ cd ~
$ git clone https://github.com/carlosV2/bash-filter.git .bash-filter

Link it to your bash profile file:

$ echo "source $(pwd)/.bash-filter/filter.sh" >> ~/.bash_profile

Usage

Once you have installed this script, you then have the function filter available to be used as a pipe. This function reads the standard input line by line and applies the specified filters to it. The output will be all those lines that match the given filters.

Filters are defined as regular parameter strings. For example, the string foo would match any text that contains foo. They are also case insensitive so foo, Foo, fOo, FOO, etc match among them.

This command appends some stats at the end. Those stats contains:

• The number of matching lines
• The total number of lines
• The number of (skipped) blank lines

If you don't want those stats to be appended you can set the $FILTER_STATS variable to false:

$ export FILTER_STATS=false

In case you want the stats but you don't want to color them you can set the $FILTER_COLORS variable to false:

$ export FILTER_COLORS=false

You can also make these variable persistent by writing them into your bash profile:

$ echo "export FILTER_STATS=false" >> ~/.bash_profile
$ echo "export FILTER_COLORS=false" >> ~/.bash_profile

• metacharacter:

---

The plus (+) metacharacter states that the given filter must be contained in the line to match it.

For example, the filter +foo will match a line if there is any occurrence of foo in it.

• metacharacter:

---

The minus (-) metacharacter states that the given filter must not be contained in the line to match it.

For example, the filter -foo will match a line if there are not occurrences of foo in it.

~ metacharacter:

The tilde (~) metacharacter states that the given filter should be searched as itself and any morphologic derivative of it.

For example, the filter ~foo will be searching for occurrences of foo and foos.

Note: Currently, this functionality is limited to the English language and singular/plural words. It is also recommended to input the word in the singular form for a better performance. However, plural words may also work. If you find an issue with this functionality, please, don't hesitate to open an issue.

= metacharacter:

The equals (=) metacharacter states that the given filter should be searched as a standalone word to match it.

For example, the filter =foo will match a line only if foo is it preceded and followed by spaces.

Combining metacharacters:

Metacharacters can be combined to form more accurate filters. However, the combination order must be as follows:

1. =
2. ~
3. +/-

Examples:

• =-foo: Will match a line if foo is not contained in as a standalone word (it might be contained as part of bigger words, though).
• =~foo: Will match a line if either foo or foos are contained as words.
• ~-foo: Will match a line if neither foo or foos are contained in it.
• +~foo: Because the combination order is broken, this filter will match a line if it contains ~foo in it (being ~ a regular character and not a metacharacter)

By default, if no + or - metacharacter is provided, the + metacharacter is applied automatically.

Examples

Imagine we have the following file:

$ cat bestsellers.txt
Fantastic Beasts and Where to Find Them - J. K. Rowling
Harry Potter and the Cursed Child - J. K. Rowling
The Girl on the Train - Paula Hawkins
Night School - Lee Child
The Reader on the 6.27 - Jean-Paul Didierlaurent
The Girl of Ink & Stars - Kiran Millwood-Hargrave
The World's Worst Children - David Walliams
The Road to Little Dribbling - Bill Bryson
Career of Evil - Robert Galbraith
Hitman Anders and the Meaning of it All - Jonas Jonasson
Lost Girls - Angela Marsons

We can filter the books that contain the:

$ cat bestsellers.txt | filter the
Fantastic Beasts and Where to Find Them - J. K. Rowling
Harry Potter and the Cursed Child - J. K. Rowling
The Girl on the Train - Paula Hawkins
The Reader on the 6.27 - Jean-Paul Didierlaurent
The Girl of Ink & Stars - Kiran Millwood-Hargrave
The World's Worst Children - David Walliams
The Road to Little Dribbling - Bill Bryson
Hitman Anders and the Meaning of it All - Jonas Jonasson

Found 8 of 11 (0 blank lines)

Alternatively, the + metacharacter can be applied with the same result:

$ cat bestsellers.txt | filter +the

This filter is matching them too but we only want to match the word the:

$ cat bestsellers.txt | filter =the
Harry Potter and the Cursed Child - J. K. Rowling
The Girl on the Train - Paula Hawkins
The Reader on the 6.27 - Jean-Paul Didierlaurent
The Girl of Ink & Stars - Kiran Millwood-Hargrave
The World's Worst Children - David Walliams
The Road to Little Dribbling - Bill Bryson
Hitman Anders and the Meaning of it All - Jonas Jonasson

Found 7 of 11 (0 blank lines)

If we don't want to match any book from J. K. Rowling, we can use:

$ cat bestsellers.txt | filter =the -rowling
The Girl on the Train - Paula Hawkins
The Reader on the 6.27 - Jean-Paul Didierlaurent
The Girl of Ink & Stars - Kiran Millwood-Hargrave
The World's Worst Children - David Walliams
The Road to Little Dribbling - Bill Bryson
Hitman Anders and the Meaning of it All - Jonas Jonasson

Found 6 of 11 (0 blank lines)

Finally, if we want to match any book about girls, we can use:

$ cat bestsellers.txt | filter ~girl
The Girl on the Train - Paula Hawkins
The Girl of Ink & Stars - Kiran Millwood-Hargrave
Lost Girls - Angela Marsons

Found 3 of 11 (0 blank lines)