问题
I want to run ack or grep on HTML files that often have very long lines. I don't want to see very long lines that wrap repeatedly. But I do want to see just that portion of a long line that surrounds a string that matches the regular expression. How can I get this using any combination of Unix tools?
回答1:
You could use the grep option -o
, possibly in combination with changing your pattern to ".{0,10}<original pattern>.{0,10}"
in order to see some context around it:
-o, --only-matching Show only the part of a matching line that matches PATTERN.
..or -c
:
-c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see below), count non-matching lines.
回答2:
Pipe your results thru cut
. I'm also considering adding a --cut
switch so you could say --cut=80
and only get 80 columns.
回答3:
You could use less as a pager for ack and chop long lines: ack --pager="less -S"
This retains the long line but leaves it on one line instead of wrapping. To see more of the line, scroll left/right in less with the arrow keys.
I have the following alias setup for ack to do this:
alias ick='ack -i --pager="less -R -S"'
回答4:
cut -c 1-100
gets characters from 1 to 100.
回答5:
Taken from: http://www.topbug.net/blog/2016/08/18/truncate-long-matching-lines-of-grep-a-solution-that-preserves-color/
The suggested approach ".{0,10}<original pattern>.{0,10}"
is perfectly good except for that the highlighting color is often messed up. I've created a script with a similar output but the color is also preserved:
#!/bin/bash
# Usage:
# grepl PATTERN [FILE]
# how many characters around the searching keyword should be shown?
context_length=10
# What is the length of the control character for the color before and after the
# matching string?
# This is mostly determined by the environmental variable GREP_COLORS.
control_length_before=$(($(echo a | grep --color=always a | cut -d a -f '1' | wc -c)-1))
control_length_after=$(($(echo a | grep --color=always a | cut -d a -f '2' | wc -c)-1))
grep -E --color=always "$1" $2 |
grep --color=none -oE \
".{0,$(($control_length_before + $context_length))}$1.{0,$(($control_length_after + $context_length))}"
Assuming the script is saved as grepl
, then grepl pattern file_with_long_lines
should display the matching lines but with only 10 characters around the matching string.
回答6:
I put the following into my .bashrc
:
grepl() {
$(which grep) --color=always $@ | less -RS
}
You can then use grepl
on the command line with any arguments that are available for grep
. Use the arrow keys to see the tail of longer lines. Use q
to quit.
Explanation:
grepl() {
: Define a new function that will be available in every (new) bash console.$(which grep)
: Get the full path ofgrep
. (Ubuntu defines an alias forgrep
that is equivalent togrep --color=auto
. We don't want that alias but the originalgrep
.)--color=always
: Colorize the output. (--color=auto
from the alias won't work sincegrep
detects that the output is put into a pipe and won't color it then.)$@
: Put all arguments given to thegrepl
function here.less
: Display the lines usingless
-R
: Show colorsS
: Don't break long lines
回答7:
Here's what I do:
function grep () {
tput rmam;
command grep "$@";
tput smam;
}
In my .bash_profile, I override grep so that it automatically runs tput rmam
before and tput smam
after, which disabled wrapping and then re-enables it.
来源:https://stackoverflow.com/questions/2034799/how-to-truncate-long-matching-lines-returned-by-grep-or-ack