How find line containing string print it + x lines after
I have a log that constantly throws data to the screen. I need to catch a line that contains a certain string, print it and the next 5 lines afterward.
It easy to do with a static file like:
grep -A 5 "XXX" /mnt/flash/logs/system/messages
grep
asked Jan 20 at 13:58
DanielDaniel
6
add a comment |
I have a log that constantly throws data to the screen. I need to catch a line that contains a certain string, print it and the next 5 lines afterward.
It easy to do with a static file like:
grep -A 5 "XXX" /mnt/flash/logs/system/messages
grep
asked Jan 20 at 13:58
DanielDaniel
6
Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09
add a comment |
I have a log that constantly throws data to the screen. I need to catch a line that contains a certain string, print it and the next 5 lines afterward.
It easy to do with a static file like:
grep -A 5 "XXX" /mnt/flash/logs/system/messages
grep
asked Jan 20 at 13:58
DanielDaniel
6
I have a log that constantly throws data to the screen. I need to catch a line that contains a certain string, print it and the next 5 lines afterward.
It easy to do with a static file like:
grep -A 5 "XXX" /mnt/flash/logs/system/messages
grep
grep
asked Jan 20 at 13:58
DanielDaniel
6
asked Jan 20 at 13:58
DanielDaniel
6
asked Jan 20 at 13:58
DanielDaniel
6
asked Jan 20 at 13:58
DanielDaniel
6
asked Jan 20 at 13:58
DanielDaniel
6
6
Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09
add a comment |
Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09
Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09
add a comment |
1 Answer
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tail -f /mnt/flash/logs/system/messages | grep -A 5 "XXX"
About tail -f:
-f
If the input file is a regular file or if the file operand specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available. […]
You already know grep -A. Note it's not portable (-A is not required by POSIX) while tail -f is.
Since it's common to rotate logs, you may find find --follow=name approach more useful. Your find may or may not support it, check man 1 find in your OS.
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
add a comment |
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1 Answer
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1 Answer
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votes
tail -f /mnt/flash/logs/system/messages | grep -A 5 "XXX"
About tail -f:
-f
If the input file is a regular file or if the file operand specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available. […]
You already know grep -A. Note it's not portable (-A is not required by POSIX) while tail -f is.
Since it's common to rotate logs, you may find find --follow=name approach more useful. Your find may or may not support it, check man 1 find in your OS.
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
add a comment |
tail -f /mnt/flash/logs/system/messages | grep -A 5 "XXX"
About tail -f:
-f
If the input file is a regular file or if the file operand specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available. […]
You already know grep -A. Note it's not portable (-A is not required by POSIX) while tail -f is.
Since it's common to rotate logs, you may find find --follow=name approach more useful. Your find may or may not support it, check man 1 find in your OS.
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
add a comment |
tail -f /mnt/flash/logs/system/messages | grep -A 5 "XXX"
About tail -f:
-f
If the input file is a regular file or if the file operand specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available. […]
You already know grep -A. Note it's not portable (-A is not required by POSIX) while tail -f is.
Since it's common to rotate logs, you may find find --follow=name approach more useful. Your find may or may not support it, check man 1 find in your OS.
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
tail -f /mnt/flash/logs/system/messages | grep -A 5 "XXX"
About tail -f:
-f
If the input file is a regular file or if the file operand specifies a FIFO, do not terminate after the last line of the input file has been copied, but read and copy further bytes from the input file when they become available. […]
You already know grep -A. Note it's not portable (-A is not required by POSIX) while tail -f is.
Since it's common to rotate logs, you may find find --follow=name approach more useful. Your find may or may not support it, check man 1 find in your OS.
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
edited Jan 20 at 14:58
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
answered Jan 20 at 14:38
Kamil MaciorowskiKamil Maciorowski
27.8k156184
27.8k156184
add a comment |
add a comment |
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Your title should say that the file keeps changing.. You show in your question that you know the answer to the question asked in your title (grep -A). But the body of the question shows that you mean for a file that is changing.
– barlop
Jan 20 at 14:07
Also, re your question, what about putting that grep line in a loop?
– barlop
Jan 20 at 14:08
Also, since you know how to print lines after a string (e.g. grep -A 5) Why don't you just ask how to find and print a line of a file that keeps changing? (And forget about asking about lines after 'cos you already know that).
– barlop
Jan 20 at 14:09