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Grepping string, but include all non-blank lines following each grep match
2019 Community Moderator ElectionHow can I grep a directory based on the contents of two successive lines?grep: Find all lines that contain Japanese kanjisBlank lines when executing “grep | xargs” in a “find -exec”How to use grep/awk/unix to match all lines from one file in another file, even if they are duplicatesRemove all the lines before the first line that contains a match?grep match all occurrences of multiple regular expressionsCompare two files and retrieve corresponding resultsregex and grep: match all letters in a listHow to search for a match, then a non-match on that line, but include context lines for matched line?How to `grep -v` and also exclude 'n' lines after the match?
Consider the following toy example:
this is a line
this line contains FOO
this line is not blank
This line also contains FOO
Some random text
This line contains FOO too
Not blank
Also not blank
More random text
FOO!
Yet more random text
FOO!
So, I want the results of a grep for FOO, but with the extra wrinkle that lines following the matching lines should be included, as long as they are not blank, and they do not themselves contain FOO. So the matches would look as follows, with the different matches separated:
MATCH 1
this line contains FOO
this line is not blank
MATCH 2
This line also contains FOO
MATCH 3
This line contains FOO too
Not blank
Also not blank
MATCH 4
FOO!
Yet more random text
MATCH 5
FOO!
Bonus points (metaphorically speaking) for a simple single line script that can be run on the command line.
ADDENDUM: Adding a running count of the match number would be quite handy, if it is not too hard.
text-processing grep
|
show 2 more comments
Consider the following toy example:
this is a line
this line contains FOO
this line is not blank
This line also contains FOO
Some random text
This line contains FOO too
Not blank
Also not blank
More random text
FOO!
Yet more random text
FOO!
So, I want the results of a grep for FOO, but with the extra wrinkle that lines following the matching lines should be included, as long as they are not blank, and they do not themselves contain FOO. So the matches would look as follows, with the different matches separated:
MATCH 1
this line contains FOO
this line is not blank
MATCH 2
This line also contains FOO
MATCH 3
This line contains FOO too
Not blank
Also not blank
MATCH 4
FOO!
Yet more random text
MATCH 5
FOO!
Bonus points (metaphorically speaking) for a simple single line script that can be run on the command line.
ADDENDUM: Adding a running count of the match number would be quite handy, if it is not too hard.
text-processing grep
1
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago
|
show 2 more comments
Consider the following toy example:
this is a line
this line contains FOO
this line is not blank
This line also contains FOO
Some random text
This line contains FOO too
Not blank
Also not blank
More random text
FOO!
Yet more random text
FOO!
So, I want the results of a grep for FOO, but with the extra wrinkle that lines following the matching lines should be included, as long as they are not blank, and they do not themselves contain FOO. So the matches would look as follows, with the different matches separated:
MATCH 1
this line contains FOO
this line is not blank
MATCH 2
This line also contains FOO
MATCH 3
This line contains FOO too
Not blank
Also not blank
MATCH 4
FOO!
Yet more random text
MATCH 5
FOO!
Bonus points (metaphorically speaking) for a simple single line script that can be run on the command line.
ADDENDUM: Adding a running count of the match number would be quite handy, if it is not too hard.
text-processing grep
Consider the following toy example:
this is a line
this line contains FOO
this line is not blank
This line also contains FOO
Some random text
This line contains FOO too
Not blank
Also not blank
More random text
FOO!
Yet more random text
FOO!
So, I want the results of a grep for FOO, but with the extra wrinkle that lines following the matching lines should be included, as long as they are not blank, and they do not themselves contain FOO. So the matches would look as follows, with the different matches separated:
MATCH 1
this line contains FOO
this line is not blank
MATCH 2
This line also contains FOO
MATCH 3
This line contains FOO too
Not blank
Also not blank
MATCH 4
FOO!
Yet more random text
MATCH 5
FOO!
Bonus points (metaphorically speaking) for a simple single line script that can be run on the command line.
ADDENDUM: Adding a running count of the match number would be quite handy, if it is not too hard.
text-processing grep
text-processing grep
edited 1 hour ago
Faheem Mitha
asked 1 hour ago
Faheem MithaFaheem Mitha
23.1k1884137
23.1k1884137
1
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago
|
show 2 more comments
1
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago
1
1
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago
|
show 2 more comments
5 Answers
5
active
oldest
votes
Using awk
rather than grep
:
awk '/FOO/ if (matching) printf("n"); matching = 1
/^$/ if (matching) printf("n"); matching = 0
matching' file
A version that enumerates the matches:
awk 'function flush_print_maybe()
if (matching) printf("Match %dn%snn", ++n, buf)
buf = ""
/FOO/ flush_print_maybe(); matching = 1
/^$/ flush_print_maybe(); matching = 0
matching buf = (buf == "" ? $0 : buf ORS $0)
END flush_print_maybe() ' file
Both awk
programs uses a very simple "state machine" to determine if it's currently matching or not matching. A match of the pattern FOO
will cause it to enter the matching
state, and a match of the pattern ^$
(an empty line) will cause it to enter the non-matching
state.
Output of empty lines between matching sets of data happens at state transitions from matching
(either into matching
or into non-matching
).
The first program prints any line when in the matching
state.
The second program collects lines in a buf
variable when in a matching
state. It flushes (empties) this after possibly printing it (depending on the state), together with a Match N
label at state transitions (when the first program would output an empty line).
Output of this last program on the sample data:
Match 1
this line contains FOO
this line is not blank
Match 2
This line also contains FOO
Match 3
This line contains FOO too
Not blank
Also not blank
Match 4
FOO!
Yet more random text
Match 5
FOO!
add a comment |
I don’t think this is doable with grep
, but it is with AWK:
#! /usr/bin/awk -f
/FOO/
matched = 1
if (notfirst) print ""
notfirst = 1
/^$/
matched = 0
matched
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
add a comment |
sed -ne '/FOO/x;P;x;/FOO/,/^$/p' testfile
Each block of non-empty lines in the output is a single chunk of matched data from the input. The number of newlines varies.
This
- suppresses output (
-n
); then - prints a blank line before every occurrence of "FOO" (
/FOO/x;P;x
- uses the empty hold space); - selects ranges of lines starting from ones containing FOO (
/FOO/
) and ending on empty lines (/^$/
); and finally - prints those lines (
p
).
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
I've included a pcregrep
solution and a python
solution.
Multiline Grep Solution
If you have pcregrep
installed, you could use a multiline pattern, such as ^.*FOO.*$n?(^.*S.*$n?)*
, e.g.:
pcregrep -M '^.*FOO.*$n?(^.*S.*$n?)*' test.txt
The subexpression ^.*FOO.*$n?
will match any line containing the string FOO
and the subexpression (^.*S.*$n?)*
will match any number of subsequent lines that containing a non-whitespace character.
Python Solution
Here is a Python script that should do what you want:
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
"""grep_follow.py
Search a text file for a pattern,
and output that pattern and the
non-empty lines which immediately follow it.
"""
import re
import sys
# Get the search pattern and the input file as command-line arguments
pattern = sys.argv[1]
input_file = sys.argv[2]
# Set a flag to determine whether or not to output the current line
print_flag = False
with open(input_file, "r") as _input_file:
# Iterate over the lines of the input file
for line in _input_file:
# Remove trailing whitespace
line = line.rstrip()
# If the line is empty, stop producing output
if not line.strip():
print_flag = False
# If the line matches the search pattern, start producing output
elif re.search(pattern, line):
print_flag = True
# If the print flag is set then output the line
if print_flag:
print(line)
You would run it like this:
$ python grep_follow.py FOO test.txt
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
Here's what I can get the output that is desired!
Match 1:
grep -iE "FOO|blank" toy.txt | head -2
Match 2:
grep -iE "FOO|blank" file.txt | grep also
Match 3:
grep -iE "FOO|blank" file.txt | tail -n 5 | head -n 3
Match 4:
grep -iE "FOO|text" file.txt | tail -n 2
Match 5:
grep -iE "FOO|text" file.txt | tail -n 1
New contributor
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
add a comment |
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5 Answers
5
active
oldest
votes
5 Answers
5
active
oldest
votes
active
oldest
votes
active
oldest
votes
Using awk
rather than grep
:
awk '/FOO/ if (matching) printf("n"); matching = 1
/^$/ if (matching) printf("n"); matching = 0
matching' file
A version that enumerates the matches:
awk 'function flush_print_maybe()
if (matching) printf("Match %dn%snn", ++n, buf)
buf = ""
/FOO/ flush_print_maybe(); matching = 1
/^$/ flush_print_maybe(); matching = 0
matching buf = (buf == "" ? $0 : buf ORS $0)
END flush_print_maybe() ' file
Both awk
programs uses a very simple "state machine" to determine if it's currently matching or not matching. A match of the pattern FOO
will cause it to enter the matching
state, and a match of the pattern ^$
(an empty line) will cause it to enter the non-matching
state.
Output of empty lines between matching sets of data happens at state transitions from matching
(either into matching
or into non-matching
).
The first program prints any line when in the matching
state.
The second program collects lines in a buf
variable when in a matching
state. It flushes (empties) this after possibly printing it (depending on the state), together with a Match N
label at state transitions (when the first program would output an empty line).
Output of this last program on the sample data:
Match 1
this line contains FOO
this line is not blank
Match 2
This line also contains FOO
Match 3
This line contains FOO too
Not blank
Also not blank
Match 4
FOO!
Yet more random text
Match 5
FOO!
add a comment |
Using awk
rather than grep
:
awk '/FOO/ if (matching) printf("n"); matching = 1
/^$/ if (matching) printf("n"); matching = 0
matching' file
A version that enumerates the matches:
awk 'function flush_print_maybe()
if (matching) printf("Match %dn%snn", ++n, buf)
buf = ""
/FOO/ flush_print_maybe(); matching = 1
/^$/ flush_print_maybe(); matching = 0
matching buf = (buf == "" ? $0 : buf ORS $0)
END flush_print_maybe() ' file
Both awk
programs uses a very simple "state machine" to determine if it's currently matching or not matching. A match of the pattern FOO
will cause it to enter the matching
state, and a match of the pattern ^$
(an empty line) will cause it to enter the non-matching
state.
Output of empty lines between matching sets of data happens at state transitions from matching
(either into matching
or into non-matching
).
The first program prints any line when in the matching
state.
The second program collects lines in a buf
variable when in a matching
state. It flushes (empties) this after possibly printing it (depending on the state), together with a Match N
label at state transitions (when the first program would output an empty line).
Output of this last program on the sample data:
Match 1
this line contains FOO
this line is not blank
Match 2
This line also contains FOO
Match 3
This line contains FOO too
Not blank
Also not blank
Match 4
FOO!
Yet more random text
Match 5
FOO!
add a comment |
Using awk
rather than grep
:
awk '/FOO/ if (matching) printf("n"); matching = 1
/^$/ if (matching) printf("n"); matching = 0
matching' file
A version that enumerates the matches:
awk 'function flush_print_maybe()
if (matching) printf("Match %dn%snn", ++n, buf)
buf = ""
/FOO/ flush_print_maybe(); matching = 1
/^$/ flush_print_maybe(); matching = 0
matching buf = (buf == "" ? $0 : buf ORS $0)
END flush_print_maybe() ' file
Both awk
programs uses a very simple "state machine" to determine if it's currently matching or not matching. A match of the pattern FOO
will cause it to enter the matching
state, and a match of the pattern ^$
(an empty line) will cause it to enter the non-matching
state.
Output of empty lines between matching sets of data happens at state transitions from matching
(either into matching
or into non-matching
).
The first program prints any line when in the matching
state.
The second program collects lines in a buf
variable when in a matching
state. It flushes (empties) this after possibly printing it (depending on the state), together with a Match N
label at state transitions (when the first program would output an empty line).
Output of this last program on the sample data:
Match 1
this line contains FOO
this line is not blank
Match 2
This line also contains FOO
Match 3
This line contains FOO too
Not blank
Also not blank
Match 4
FOO!
Yet more random text
Match 5
FOO!
Using awk
rather than grep
:
awk '/FOO/ if (matching) printf("n"); matching = 1
/^$/ if (matching) printf("n"); matching = 0
matching' file
A version that enumerates the matches:
awk 'function flush_print_maybe()
if (matching) printf("Match %dn%snn", ++n, buf)
buf = ""
/FOO/ flush_print_maybe(); matching = 1
/^$/ flush_print_maybe(); matching = 0
matching buf = (buf == "" ? $0 : buf ORS $0)
END flush_print_maybe() ' file
Both awk
programs uses a very simple "state machine" to determine if it's currently matching or not matching. A match of the pattern FOO
will cause it to enter the matching
state, and a match of the pattern ^$
(an empty line) will cause it to enter the non-matching
state.
Output of empty lines between matching sets of data happens at state transitions from matching
(either into matching
or into non-matching
).
The first program prints any line when in the matching
state.
The second program collects lines in a buf
variable when in a matching
state. It flushes (empties) this after possibly printing it (depending on the state), together with a Match N
label at state transitions (when the first program would output an empty line).
Output of this last program on the sample data:
Match 1
this line contains FOO
this line is not blank
Match 2
This line also contains FOO
Match 3
This line contains FOO too
Not blank
Also not blank
Match 4
FOO!
Yet more random text
Match 5
FOO!
edited 57 mins ago
answered 1 hour ago
KusalanandaKusalananda
136k17257426
136k17257426
add a comment |
add a comment |
I don’t think this is doable with grep
, but it is with AWK:
#! /usr/bin/awk -f
/FOO/
matched = 1
if (notfirst) print ""
notfirst = 1
/^$/
matched = 0
matched
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
add a comment |
I don’t think this is doable with grep
, but it is with AWK:
#! /usr/bin/awk -f
/FOO/
matched = 1
if (notfirst) print ""
notfirst = 1
/^$/
matched = 0
matched
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
add a comment |
I don’t think this is doable with grep
, but it is with AWK:
#! /usr/bin/awk -f
/FOO/
matched = 1
if (notfirst) print ""
notfirst = 1
/^$/
matched = 0
matched
I don’t think this is doable with grep
, but it is with AWK:
#! /usr/bin/awk -f
/FOO/
matched = 1
if (notfirst) print ""
notfirst = 1
/^$/
matched = 0
matched
edited 58 mins ago
answered 1 hour ago
Stephen KittStephen Kitt
177k24402479
177k24402479
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
add a comment |
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
at the start of the output, period, right?
– ilkkachu
1 hour ago
at the start of the output, period, right?
– ilkkachu
1 hour ago
1
1
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
At the start of the output, yes; I’ve fixed that.
– Stephen Kitt
57 mins ago
add a comment |
sed -ne '/FOO/x;P;x;/FOO/,/^$/p' testfile
Each block of non-empty lines in the output is a single chunk of matched data from the input. The number of newlines varies.
This
- suppresses output (
-n
); then - prints a blank line before every occurrence of "FOO" (
/FOO/x;P;x
- uses the empty hold space); - selects ranges of lines starting from ones containing FOO (
/FOO/
) and ending on empty lines (/^$/
); and finally - prints those lines (
p
).
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
sed -ne '/FOO/x;P;x;/FOO/,/^$/p' testfile
Each block of non-empty lines in the output is a single chunk of matched data from the input. The number of newlines varies.
This
- suppresses output (
-n
); then - prints a blank line before every occurrence of "FOO" (
/FOO/x;P;x
- uses the empty hold space); - selects ranges of lines starting from ones containing FOO (
/FOO/
) and ending on empty lines (/^$/
); and finally - prints those lines (
p
).
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
sed -ne '/FOO/x;P;x;/FOO/,/^$/p' testfile
Each block of non-empty lines in the output is a single chunk of matched data from the input. The number of newlines varies.
This
- suppresses output (
-n
); then - prints a blank line before every occurrence of "FOO" (
/FOO/x;P;x
- uses the empty hold space); - selects ranges of lines starting from ones containing FOO (
/FOO/
) and ending on empty lines (/^$/
); and finally - prints those lines (
p
).
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
sed -ne '/FOO/x;P;x;/FOO/,/^$/p' testfile
Each block of non-empty lines in the output is a single chunk of matched data from the input. The number of newlines varies.
This
- suppresses output (
-n
); then - prints a blank line before every occurrence of "FOO" (
/FOO/x;P;x
- uses the empty hold space); - selects ranges of lines starting from ones containing FOO (
/FOO/
) and ending on empty lines (/^$/
); and finally - prints those lines (
p
).
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
edited 48 mins ago
answered 1 hour ago
Michael HomerMichael Homer
49.9k8137175
49.9k8137175
add a comment |
add a comment |
I've included a pcregrep
solution and a python
solution.
Multiline Grep Solution
If you have pcregrep
installed, you could use a multiline pattern, such as ^.*FOO.*$n?(^.*S.*$n?)*
, e.g.:
pcregrep -M '^.*FOO.*$n?(^.*S.*$n?)*' test.txt
The subexpression ^.*FOO.*$n?
will match any line containing the string FOO
and the subexpression (^.*S.*$n?)*
will match any number of subsequent lines that containing a non-whitespace character.
Python Solution
Here is a Python script that should do what you want:
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
"""grep_follow.py
Search a text file for a pattern,
and output that pattern and the
non-empty lines which immediately follow it.
"""
import re
import sys
# Get the search pattern and the input file as command-line arguments
pattern = sys.argv[1]
input_file = sys.argv[2]
# Set a flag to determine whether or not to output the current line
print_flag = False
with open(input_file, "r") as _input_file:
# Iterate over the lines of the input file
for line in _input_file:
# Remove trailing whitespace
line = line.rstrip()
# If the line is empty, stop producing output
if not line.strip():
print_flag = False
# If the line matches the search pattern, start producing output
elif re.search(pattern, line):
print_flag = True
# If the print flag is set then output the line
if print_flag:
print(line)
You would run it like this:
$ python grep_follow.py FOO test.txt
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
I've included a pcregrep
solution and a python
solution.
Multiline Grep Solution
If you have pcregrep
installed, you could use a multiline pattern, such as ^.*FOO.*$n?(^.*S.*$n?)*
, e.g.:
pcregrep -M '^.*FOO.*$n?(^.*S.*$n?)*' test.txt
The subexpression ^.*FOO.*$n?
will match any line containing the string FOO
and the subexpression (^.*S.*$n?)*
will match any number of subsequent lines that containing a non-whitespace character.
Python Solution
Here is a Python script that should do what you want:
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
"""grep_follow.py
Search a text file for a pattern,
and output that pattern and the
non-empty lines which immediately follow it.
"""
import re
import sys
# Get the search pattern and the input file as command-line arguments
pattern = sys.argv[1]
input_file = sys.argv[2]
# Set a flag to determine whether or not to output the current line
print_flag = False
with open(input_file, "r") as _input_file:
# Iterate over the lines of the input file
for line in _input_file:
# Remove trailing whitespace
line = line.rstrip()
# If the line is empty, stop producing output
if not line.strip():
print_flag = False
# If the line matches the search pattern, start producing output
elif re.search(pattern, line):
print_flag = True
# If the print flag is set then output the line
if print_flag:
print(line)
You would run it like this:
$ python grep_follow.py FOO test.txt
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
add a comment |
I've included a pcregrep
solution and a python
solution.
Multiline Grep Solution
If you have pcregrep
installed, you could use a multiline pattern, such as ^.*FOO.*$n?(^.*S.*$n?)*
, e.g.:
pcregrep -M '^.*FOO.*$n?(^.*S.*$n?)*' test.txt
The subexpression ^.*FOO.*$n?
will match any line containing the string FOO
and the subexpression (^.*S.*$n?)*
will match any number of subsequent lines that containing a non-whitespace character.
Python Solution
Here is a Python script that should do what you want:
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
"""grep_follow.py
Search a text file for a pattern,
and output that pattern and the
non-empty lines which immediately follow it.
"""
import re
import sys
# Get the search pattern and the input file as command-line arguments
pattern = sys.argv[1]
input_file = sys.argv[2]
# Set a flag to determine whether or not to output the current line
print_flag = False
with open(input_file, "r") as _input_file:
# Iterate over the lines of the input file
for line in _input_file:
# Remove trailing whitespace
line = line.rstrip()
# If the line is empty, stop producing output
if not line.strip():
print_flag = False
# If the line matches the search pattern, start producing output
elif re.search(pattern, line):
print_flag = True
# If the print flag is set then output the line
if print_flag:
print(line)
You would run it like this:
$ python grep_follow.py FOO test.txt
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
I've included a pcregrep
solution and a python
solution.
Multiline Grep Solution
If you have pcregrep
installed, you could use a multiline pattern, such as ^.*FOO.*$n?(^.*S.*$n?)*
, e.g.:
pcregrep -M '^.*FOO.*$n?(^.*S.*$n?)*' test.txt
The subexpression ^.*FOO.*$n?
will match any line containing the string FOO
and the subexpression (^.*S.*$n?)*
will match any number of subsequent lines that containing a non-whitespace character.
Python Solution
Here is a Python script that should do what you want:
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
"""grep_follow.py
Search a text file for a pattern,
and output that pattern and the
non-empty lines which immediately follow it.
"""
import re
import sys
# Get the search pattern and the input file as command-line arguments
pattern = sys.argv[1]
input_file = sys.argv[2]
# Set a flag to determine whether or not to output the current line
print_flag = False
with open(input_file, "r") as _input_file:
# Iterate over the lines of the input file
for line in _input_file:
# Remove trailing whitespace
line = line.rstrip()
# If the line is empty, stop producing output
if not line.strip():
print_flag = False
# If the line matches the search pattern, start producing output
elif re.search(pattern, line):
print_flag = True
# If the print flag is set then output the line
if print_flag:
print(line)
You would run it like this:
$ python grep_follow.py FOO test.txt
this line contains FOO
this line is not blank
This line also contains FOO
This line contains FOO too
Not blank
Also not blank
FOO!
Yet more random text
FOO!
edited 1 hour ago
answered 1 hour ago
igaligal
5,9311536
5,9311536
add a comment |
add a comment |
Here's what I can get the output that is desired!
Match 1:
grep -iE "FOO|blank" toy.txt | head -2
Match 2:
grep -iE "FOO|blank" file.txt | grep also
Match 3:
grep -iE "FOO|blank" file.txt | tail -n 5 | head -n 3
Match 4:
grep -iE "FOO|text" file.txt | tail -n 2
Match 5:
grep -iE "FOO|text" file.txt | tail -n 1
New contributor
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
add a comment |
Here's what I can get the output that is desired!
Match 1:
grep -iE "FOO|blank" toy.txt | head -2
Match 2:
grep -iE "FOO|blank" file.txt | grep also
Match 3:
grep -iE "FOO|blank" file.txt | tail -n 5 | head -n 3
Match 4:
grep -iE "FOO|text" file.txt | tail -n 2
Match 5:
grep -iE "FOO|text" file.txt | tail -n 1
New contributor
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
add a comment |
Here's what I can get the output that is desired!
Match 1:
grep -iE "FOO|blank" toy.txt | head -2
Match 2:
grep -iE "FOO|blank" file.txt | grep also
Match 3:
grep -iE "FOO|blank" file.txt | tail -n 5 | head -n 3
Match 4:
grep -iE "FOO|text" file.txt | tail -n 2
Match 5:
grep -iE "FOO|text" file.txt | tail -n 1
New contributor
Here's what I can get the output that is desired!
Match 1:
grep -iE "FOO|blank" toy.txt | head -2
Match 2:
grep -iE "FOO|blank" file.txt | grep also
Match 3:
grep -iE "FOO|blank" file.txt | tail -n 5 | head -n 3
Match 4:
grep -iE "FOO|text" file.txt | tail -n 2
Match 5:
grep -iE "FOO|text" file.txt | tail -n 1
New contributor
edited 1 hour ago
New contributor
answered 1 hour ago
Vivek KanadiyaVivek Kanadiya
1547
1547
New contributor
New contributor
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
add a comment |
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
This assumes knowledge of the contents of the file.
– Kusalananda
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
yes this is based on knowledge of file
– Vivek Kanadiya
1 hour ago
1
1
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
@VivekKanadiya, I think the point here, as often in computing, is to automate a task so that it can be done automatically for multiple sets of data. A solution that only works for one particular input is hardly useful, instead of writing a set of commands to produce the output, we could just copy the required lines by hand. Note that the question also says, right there in the start, that the input shown is "a toy example".
– ilkkachu
1 hour ago
add a comment |
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1
do you want all the Matches in one output or you want them to be ran separately ?
– Vivek Kanadiya
1 hour ago
I guess one output is fine, as long as they are clearly separated, say by a blank line.
– Faheem Mitha
1 hour ago
might not possible in one output but I can try to see in each separate output!
– Vivek Kanadiya
1 hour ago
For matches 4 & 5, the simple logic could say "I've matched (the 4th) "FOO", so I should continue printing in this matching block until I see a blank line, and so the final "FOO" is included in this block", but i see you've separated it -- because it's a separate "FOO" match. Do you require the 5th "FOO" to be printed separately?
– Jeff Schaller
1 hour ago
@JeffSchaller Yes, please separate different FOO matches.
– Faheem Mitha
1 hour ago