Copyright (c) 2015 Will Roberts <[email protected]>
Licensed under the MIT License (see file LICENSE.rst
for
details).
Search and replace on file(s), with matching on fixed strings.
fsed
is a tool specially designed for situations where you have to
do many string search-and-replace operations with fixed strings
(that is, fsed
doesn't do regular expressions). By doing all the
searching and replacing on all the patterns at the same time, fsed
can be much faster than tools that do string rewriting one pattern at
a time (like one-liners in sed
or perl
).
To do its searching, fsed
uses the Aho-Corasick algorithm,
which is a very clever way of matching multiple patterns at the same
time, and was used to implement the original fgrep Unix utility
(now accessed as grep -F
). This algorithm is capable of finding
matches which overlap each other, and in these cases, fsed
must
choose which matches to rewrite. The policy adopted by fsed
is to
be greedy, and always rewrite the shortest, leftmost match first.
For illustration, imagine a situation where we would like to rewrite
a
with b
, aa
with c
, and aaa
with d
. What
should we do when we see the input string aaa
? Should we produce
bbb
, bc
, cb
, or d
? fsed
produces bbb
in this
case.
fsed
is written in Python; you can install it with pip:
pip install fsed
fsed [OPTIONS] PATTERN_FILE [INPUT_FILE [INPUT_FILE2 ...]]
If one or more INPUT_FILEs
are specified, fsed
reads and
concatenates these as its input; otherwise, fsed
reads the
standard input.
Options:
--pattern-format=FMT
- Set FMT to
tsv
orsed
(default issed
) to specify the format ofPATTERN_FILE
. -o/--output=OUTFILE
- Specifies that the program output should be written to
OUTFILE
. If this option is not used,fsed
writes to standard output. -w/--words
- Makes
fsed
match only on word boundaries; this flag instructsfsed
to append\b
to the beginning and end of every pattern inPATTERN_FILE
. --by-line/--across-lines
- Sets whether
fsed
should process the input line by line or character by character; the default is--across-lines
. --slow
- Indicates that
fsed
should try very hard to always find the longest matches on the input; this is very slow, and forces--by-line
to be on. -q
- Quiet operation, do not emit warnings.
-v/--verbose
- Turns on debugging output.
Note: fsed
runs even faster using PyPy:
pypy -m fsed.fsed [OPTIONS] PATTERN_FILE [INPUT_FILE [INPUT_FILE2 ...]]
PATTERN_FILE
contains a list of patterns to search and replace in
the input; each pattern is listed on a separate line. fsed
supports two formats for specifying patterns. The default, sed
,
specifies strings and their replacements the way the sed
utility
does:
s/SEARCH/REPLACE/
The character following the s
character is the pattern delimiter,
and can be any character (it does not have to be a forward slash).
The other format, tsv
, specifies patterns using <TAB>
characters as delimiters:
SEARCH<TAB>REPLACE
In this format, there must be only one <TAB>
character per line.
Patterns can contain escape characters:
\\
- Backslash (\)
\a
- ASCII bell (BEL)
\b
- Word boundary
\f
- ASCII formfeed (FF)
\n
- ASCII linefeed (LF)
\r
- Carriage Return (CR)
\t
- Horizontal Tab (TAB)
\v
- ASCII vertical tab (VT)