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Bash method for viewing beginning and end of file
Command to display first few and last few lines of a fileRace Condition for Shell Blocks in Bash?Add character to beginning and end of columnHow to transform two delimited ASCII filesusing awk to create a LaTex table from my data in a text fileAppend columns in a text file to after the final rowRemove spaces and headers from a dumped database tableCount the maximum character length for all the data fields in a simplified csv file and output to txtWriting a program for editing .txt data - Python or Unix?Merging two Unix filesegrep regular expression - same word in the beginning and endhow to evaluate number between a range of numbers using different variables in bash
On queue-based clusters the Queue of pending jobs is shown from a command, say showqueue.
The command returns, in columns, a list of reasonable data like names, etc, but the columns/data don't really matter for the question.
I like using the utility watch like watch showqueue at times (with an alias of alias watch="watch " to force alias expansion of my command to watch). There is valuable data (Running jobs), in the first few lines, then pending jobs, etc, and some valuable summaries at the end.
However, at times the output of showqueue goes off the screen (Unbelievable, I know)! Ideally, I'd like some way to be able to see the beginning and end of the file at the same time.
The best I have so far is: showqueue > file; head -n 20 file > file2; echo "..." >> file2 ; tail -n 20 file >> file2; cat file2, and using watch on an alias of that.
Does anyone know of anything a little more flexible or single-utility? My solution gets a little nastier with bash loops to make the "..." break multilined, it's not adaptive to resizing the terminal window at all, and I'm sure there's more that I missed.
Any suggestions?
bash text-processing
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
add a comment |
On queue-based clusters the Queue of pending jobs is shown from a command, say showqueue.
The command returns, in columns, a list of reasonable data like names, etc, but the columns/data don't really matter for the question.
I like using the utility watch like watch showqueue at times (with an alias of alias watch="watch " to force alias expansion of my command to watch). There is valuable data (Running jobs), in the first few lines, then pending jobs, etc, and some valuable summaries at the end.
However, at times the output of showqueue goes off the screen (Unbelievable, I know)! Ideally, I'd like some way to be able to see the beginning and end of the file at the same time.
The best I have so far is: showqueue > file; head -n 20 file > file2; echo "..." >> file2 ; tail -n 20 file >> file2; cat file2, and using watch on an alias of that.
Does anyone know of anything a little more flexible or single-utility? My solution gets a little nastier with bash loops to make the "..." break multilined, it's not adaptive to resizing the terminal window at all, and I'm sure there's more that I missed.
Any suggestions?
bash text-processing
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
2
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (tryseq 30 | (head && tail)for instance).
– Stéphane Chazelas
Mar 26 at 20:16
2
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24
add a comment |
On queue-based clusters the Queue of pending jobs is shown from a command, say showqueue.
The command returns, in columns, a list of reasonable data like names, etc, but the columns/data don't really matter for the question.
I like using the utility watch like watch showqueue at times (with an alias of alias watch="watch " to force alias expansion of my command to watch). There is valuable data (Running jobs), in the first few lines, then pending jobs, etc, and some valuable summaries at the end.
However, at times the output of showqueue goes off the screen (Unbelievable, I know)! Ideally, I'd like some way to be able to see the beginning and end of the file at the same time.
The best I have so far is: showqueue > file; head -n 20 file > file2; echo "..." >> file2 ; tail -n 20 file >> file2; cat file2, and using watch on an alias of that.
Does anyone know of anything a little more flexible or single-utility? My solution gets a little nastier with bash loops to make the "..." break multilined, it's not adaptive to resizing the terminal window at all, and I'm sure there's more that I missed.
Any suggestions?
bash text-processing
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
On queue-based clusters the Queue of pending jobs is shown from a command, say showqueue.
The command returns, in columns, a list of reasonable data like names, etc, but the columns/data don't really matter for the question.
I like using the utility watch like watch showqueue at times (with an alias of alias watch="watch " to force alias expansion of my command to watch). There is valuable data (Running jobs), in the first few lines, then pending jobs, etc, and some valuable summaries at the end.
However, at times the output of showqueue goes off the screen (Unbelievable, I know)! Ideally, I'd like some way to be able to see the beginning and end of the file at the same time.
The best I have so far is: showqueue > file; head -n 20 file > file2; echo "..." >> file2 ; tail -n 20 file >> file2; cat file2, and using watch on an alias of that.
Does anyone know of anything a little more flexible or single-utility? My solution gets a little nastier with bash loops to make the "..." break multilined, it's not adaptive to resizing the terminal window at all, and I'm sure there's more that I missed.
Any suggestions?
bash text-processing
bash text-processing
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
edited Mar 26 at 19:11
Rui F Ribeiro
41.9k1483142
41.9k1483142
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
asked Mar 26 at 19:05
MadisonCooperMadisonCooper
414
414
Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
2
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (tryseq 30 | (head && tail)for instance).
– Stéphane Chazelas
Mar 26 at 20:16
2
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24
add a comment |
Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
2
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (tryseq 30 | (head && tail)for instance).
– Stéphane Chazelas
Mar 26 at 20:16
2
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24
Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
2
2
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (try
seq 30 | (head && tail) for instance).– Stéphane Chazelas
Mar 26 at 20:16
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (try
seq 30 | (head && tail) for instance).– Stéphane Chazelas
Mar 26 at 20:16
2
2
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24
add a comment |
4 Answers
4
active
oldest
votes
Are you looking to do something like the following? Shows output from both head and tail.
$ showqueue | (head && tail)
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
5
Some implementations ofheadmay read more than 10 lines and leave nothing fortailto read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Usehead; echo '...'; tailto get the dots in there as well.
– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement forheadto not over-read? (same on Mac, it seems to read by blocks)
– ilkkachu
Mar 26 at 19:22
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The onlyheadimplementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93'sheadbuiltin.
– Stéphane Chazelas
Mar 26 at 20:04
|
show 3 more comments
awk solution for an arbitrary number of lines shown from the head and the tail (change n=3 to set the amount):
$ seq 99999 | awk -v n=3 'NR <= n; NR > n a[NR] = $0; delete a[NR-n];
END print "..."; for (i = NR-n+1; i <= NR; i++) if (i in a) print a[i]; '
1
2
3
...
99997
99998
99999
As it's written, the head and tail parts will not overlap, even if the input is shorter than 2*n lines.
In some awk implementations, using for (x in a) print a[x]; in the END part also works. But in general, it's not guaranteed to return the array entries in the correct order, and doesn't in e.g. mawk.
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
Ifmis the number of lines in the file, andm < 2n, that will print2n - mempty lines. Also have look here ;-).for (x in a)will iterate in order only in GNU awk; if you think that it works inmawktoo, test with > 10 values.
– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizingx in awasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!
– ilkkachu
Mar 26 at 20:42
add a comment |
Using the same approach as you, using a temporary file, but doing it slightly shorter:
showqueue >/tmp/q.out; head -n 20 /tmp/q.out; echo '...'; tail -n 20 /tmp/q.out
This would not suffer from the same issues as discussed under another answer, but would possibly show the same lines twice if the output was shorter than 40 lines.
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
add a comment |
You can use simple awk script. Added circle buffer there n=3 is for last 3 lines
awk 'NR<=n print $0 A[NR%n]=$0 END for (i=1; i<=n; ++i) if (NR+i>2*n)print A[(NR+i)%n] ' n=3 < <( seq 10 )
After update its not simple anymore though,
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
1
This would only show the first and last line. To show more than that, you would have to changeNR==1toNR <= 10(or something), and then collect lines into a (circular?) buffer that you later output in theENDblock.
– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
Are you looking to do something like the following? Shows output from both head and tail.
$ showqueue | (head && tail)
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
5
Some implementations ofheadmay read more than 10 lines and leave nothing fortailto read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Usehead; echo '...'; tailto get the dots in there as well.
– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement forheadto not over-read? (same on Mac, it seems to read by blocks)
– ilkkachu
Mar 26 at 19:22
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The onlyheadimplementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93'sheadbuiltin.
– Stéphane Chazelas
Mar 26 at 20:04
|
show 3 more comments
Are you looking to do something like the following? Shows output from both head and tail.
$ showqueue | (head && tail)
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
5
Some implementations ofheadmay read more than 10 lines and leave nothing fortailto read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Usehead; echo '...'; tailto get the dots in there as well.
– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement forheadto not over-read? (same on Mac, it seems to read by blocks)
– ilkkachu
Mar 26 at 19:22
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The onlyheadimplementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93'sheadbuiltin.
– Stéphane Chazelas
Mar 26 at 20:04
|
show 3 more comments
Are you looking to do something like the following? Shows output from both head and tail.
$ showqueue | (head && tail)
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
Are you looking to do something like the following? Shows output from both head and tail.
$ showqueue | (head && tail)
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
answered Mar 26 at 19:16
Timothy PulliamTimothy Pulliam
1,3951025
1,3951025
5
Some implementations ofheadmay read more than 10 lines and leave nothing fortailto read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Usehead; echo '...'; tailto get the dots in there as well.
– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement forheadto not over-read? (same on Mac, it seems to read by blocks)
– ilkkachu
Mar 26 at 19:22
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The onlyheadimplementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93'sheadbuiltin.
– Stéphane Chazelas
Mar 26 at 20:04
|
show 3 more comments
5
Some implementations ofheadmay read more than 10 lines and leave nothing fortailto read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Usehead; echo '...'; tailto get the dots in there as well.
– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement forheadto not over-read? (same on Mac, it seems to read by blocks)
– ilkkachu
Mar 26 at 19:22
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The onlyheadimplementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93'sheadbuiltin.
– Stéphane Chazelas
Mar 26 at 20:04
5
5
Some implementations of
head may read more than 10 lines and leave nothing for tail to read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Use head; echo '...'; tail to get the dots in there as well.– Kusalananda♦
Mar 26 at 19:18
Some implementations of
head may read more than 10 lines and leave nothing for tail to read. The utility is not supposed to do that and I believe that the GNU tools are well behave in this respect. Use head; echo '...'; tail to get the dots in there as well.– Kusalananda♦
Mar 26 at 19:18
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
Yeah, combined with @Kusalananda's comment it's much more succinct than my solution. I'll mark as correct for now! Thanks.
– MadisonCooper
Mar 26 at 19:22
4
4
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement for
head to not over-read? (same on Mac, it seems to read by blocks)– ilkkachu
Mar 26 at 19:22
@Kusalananda, nope, on my system, GNU head (coreutils 8.26) reads blocks of 8192 bytes. It does try to seek back, but obviously can't in case of a pipe. Though anyway, is there really a requirement for
head to not over-read? (same on Mac, it seems to read by blocks)– ilkkachu
Mar 26 at 19:22
2
2
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
@ilkkachu yeah, even as it stands the tail part is occasionally blank even on sufficiently long output (I know since I'm using head -n 35, and that's full), but fortunately it's just a convenience to watch and I can wait 3 seconds for a refresh if needed.
– MadisonCooper
Mar 26 at 19:27
3
3
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The only
head implementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93's head builtin.– Stéphane Chazelas
Mar 26 at 20:04
@Kusalananda, POSIX allows implementations to do that when the input is not seekable and most implementations do. Not doing it would mean reading one byte at a time which would be very inefficient (or put the data back onto the pipe where supported which would cause all sorts of different problems). The only
head implementation I know that reads one byte at a time to avoid reading past the 10th newline is ksh93's head builtin.– Stéphane Chazelas
Mar 26 at 20:04
|
show 3 more comments
awk solution for an arbitrary number of lines shown from the head and the tail (change n=3 to set the amount):
$ seq 99999 | awk -v n=3 'NR <= n; NR > n a[NR] = $0; delete a[NR-n];
END print "..."; for (i = NR-n+1; i <= NR; i++) if (i in a) print a[i]; '
1
2
3
...
99997
99998
99999
As it's written, the head and tail parts will not overlap, even if the input is shorter than 2*n lines.
In some awk implementations, using for (x in a) print a[x]; in the END part also works. But in general, it's not guaranteed to return the array entries in the correct order, and doesn't in e.g. mawk.
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
Ifmis the number of lines in the file, andm < 2n, that will print2n - mempty lines. Also have look here ;-).for (x in a)will iterate in order only in GNU awk; if you think that it works inmawktoo, test with > 10 values.
– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizingx in awasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!
– ilkkachu
Mar 26 at 20:42
add a comment |
awk solution for an arbitrary number of lines shown from the head and the tail (change n=3 to set the amount):
$ seq 99999 | awk -v n=3 'NR <= n; NR > n a[NR] = $0; delete a[NR-n];
END print "..."; for (i = NR-n+1; i <= NR; i++) if (i in a) print a[i]; '
1
2
3
...
99997
99998
99999
As it's written, the head and tail parts will not overlap, even if the input is shorter than 2*n lines.
In some awk implementations, using for (x in a) print a[x]; in the END part also works. But in general, it's not guaranteed to return the array entries in the correct order, and doesn't in e.g. mawk.
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
Ifmis the number of lines in the file, andm < 2n, that will print2n - mempty lines. Also have look here ;-).for (x in a)will iterate in order only in GNU awk; if you think that it works inmawktoo, test with > 10 values.
– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizingx in awasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!
– ilkkachu
Mar 26 at 20:42
add a comment |
awk solution for an arbitrary number of lines shown from the head and the tail (change n=3 to set the amount):
$ seq 99999 | awk -v n=3 'NR <= n; NR > n a[NR] = $0; delete a[NR-n];
END print "..."; for (i = NR-n+1; i <= NR; i++) if (i in a) print a[i]; '
1
2
3
...
99997
99998
99999
As it's written, the head and tail parts will not overlap, even if the input is shorter than 2*n lines.
In some awk implementations, using for (x in a) print a[x]; in the END part also works. But in general, it's not guaranteed to return the array entries in the correct order, and doesn't in e.g. mawk.
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
awk solution for an arbitrary number of lines shown from the head and the tail (change n=3 to set the amount):
$ seq 99999 | awk -v n=3 'NR <= n; NR > n a[NR] = $0; delete a[NR-n];
END print "..."; for (i = NR-n+1; i <= NR; i++) if (i in a) print a[i]; '
1
2
3
...
99997
99998
99999
As it's written, the head and tail parts will not overlap, even if the input is shorter than 2*n lines.
In some awk implementations, using for (x in a) print a[x]; in the END part also works. But in general, it's not guaranteed to return the array entries in the correct order, and doesn't in e.g. mawk.
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
edited Mar 26 at 20:37
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
answered Mar 26 at 19:33
ilkkachuilkkachu
63k10103180
63k10103180
Ifmis the number of lines in the file, andm < 2n, that will print2n - mempty lines. Also have look here ;-).for (x in a)will iterate in order only in GNU awk; if you think that it works inmawktoo, test with > 10 values.
– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizingx in awasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!
– ilkkachu
Mar 26 at 20:42
add a comment |
Ifmis the number of lines in the file, andm < 2n, that will print2n - mempty lines. Also have look here ;-).for (x in a)will iterate in order only in GNU awk; if you think that it works inmawktoo, test with > 10 values.
– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizingx in awasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!
– ilkkachu
Mar 26 at 20:42
If
m is the number of lines in the file, and m < 2n, that will print 2n - m empty lines. Also have look here ;-). for (x in a) will iterate in order only in GNU awk; if you think that it works in mawk too, test with > 10 values.– mosvy
Mar 26 at 20:31
If
m is the number of lines in the file, and m < 2n, that will print 2n - m empty lines. Also have look here ;-). for (x in a) will iterate in order only in GNU awk; if you think that it works in mawk too, test with > 10 values.– mosvy
Mar 26 at 20:31
@mosvy, oh, whoops, I forgot to re-check that after realizing
x in a wasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!– ilkkachu
Mar 26 at 20:42
@mosvy, oh, whoops, I forgot to re-check that after realizing
x in a wasn't right. Fixed now, thanks. There's also another awk answer in the question Stéphane linked to. I like the modulo trick, though!– ilkkachu
Mar 26 at 20:42
add a comment |
Using the same approach as you, using a temporary file, but doing it slightly shorter:
showqueue >/tmp/q.out; head -n 20 /tmp/q.out; echo '...'; tail -n 20 /tmp/q.out
This would not suffer from the same issues as discussed under another answer, but would possibly show the same lines twice if the output was shorter than 40 lines.
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
add a comment |
Using the same approach as you, using a temporary file, but doing it slightly shorter:
showqueue >/tmp/q.out; head -n 20 /tmp/q.out; echo '...'; tail -n 20 /tmp/q.out
This would not suffer from the same issues as discussed under another answer, but would possibly show the same lines twice if the output was shorter than 40 lines.
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
add a comment |
Using the same approach as you, using a temporary file, but doing it slightly shorter:
showqueue >/tmp/q.out; head -n 20 /tmp/q.out; echo '...'; tail -n 20 /tmp/q.out
This would not suffer from the same issues as discussed under another answer, but would possibly show the same lines twice if the output was shorter than 40 lines.
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
Using the same approach as you, using a temporary file, but doing it slightly shorter:
showqueue >/tmp/q.out; head -n 20 /tmp/q.out; echo '...'; tail -n 20 /tmp/q.out
This would not suffer from the same issues as discussed under another answer, but would possibly show the same lines twice if the output was shorter than 40 lines.
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
edited Mar 26 at 19:46
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
answered Mar 26 at 19:30
Kusalananda♦Kusalananda
139k17261433
139k17261433
add a comment |
add a comment |
You can use simple awk script. Added circle buffer there n=3 is for last 3 lines
awk 'NR<=n print $0 A[NR%n]=$0 END for (i=1; i<=n; ++i) if (NR+i>2*n)print A[(NR+i)%n] ' n=3 < <( seq 10 )
After update its not simple anymore though,
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
1
This would only show the first and last line. To show more than that, you would have to changeNR==1toNR <= 10(or something), and then collect lines into a (circular?) buffer that you later output in theENDblock.
– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
add a comment |
You can use simple awk script. Added circle buffer there n=3 is for last 3 lines
awk 'NR<=n print $0 A[NR%n]=$0 END for (i=1; i<=n; ++i) if (NR+i>2*n)print A[(NR+i)%n] ' n=3 < <( seq 10 )
After update its not simple anymore though,
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
1
This would only show the first and last line. To show more than that, you would have to changeNR==1toNR <= 10(or something), and then collect lines into a (circular?) buffer that you later output in theENDblock.
– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
add a comment |
You can use simple awk script. Added circle buffer there n=3 is for last 3 lines
awk 'NR<=n print $0 A[NR%n]=$0 END for (i=1; i<=n; ++i) if (NR+i>2*n)print A[(NR+i)%n] ' n=3 < <( seq 10 )
After update its not simple anymore though,
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
You can use simple awk script. Added circle buffer there n=3 is for last 3 lines
awk 'NR<=n print $0 A[NR%n]=$0 END for (i=1; i<=n; ++i) if (NR+i>2*n)print A[(NR+i)%n] ' n=3 < <( seq 10 )
After update its not simple anymore though,
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
edited Mar 27 at 7:22
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
answered Mar 26 at 19:25
AbdurrahimAbdurrahim
1012
1012
1
This would only show the first and last line. To show more than that, you would have to changeNR==1toNR <= 10(or something), and then collect lines into a (circular?) buffer that you later output in theENDblock.
– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
add a comment |
1
This would only show the first and last line. To show more than that, you would have to changeNR==1toNR <= 10(or something), and then collect lines into a (circular?) buffer that you later output in theENDblock.
– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
1
1
This would only show the first and last line. To show more than that, you would have to change
NR==1 to NR <= 10 (or something), and then collect lines into a (circular?) buffer that you later output in the END block.– Kusalananda♦
Mar 26 at 19:32
This would only show the first and last line. To show more than that, you would have to change
NR==1 to NR <= 10 (or something), and then collect lines into a (circular?) buffer that you later output in the END block.– Kusalananda♦
Mar 26 at 19:32
yes let me update
– Abdurrahim
Mar 26 at 19:43
yes let me update
– Abdurrahim
Mar 26 at 19:43
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
This will print some lines twice when then the number of lines is less than 2 * n.
– mosvy
Mar 26 at 20:39
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
:) ok adding that as well now I am curious what you will find next :D
– Abdurrahim
Mar 27 at 7:22
add a comment |
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Closed as duplicate, but the question only shares similarities (Mine is more about a command, I learned, and not files), and the answers here didn't show up there, but if you insist
– MadisonCooper
Mar 26 at 19:59
2
Fair enough. I've reopened. Note that the answer that you have accepted will only work for large outputs as noted at my answer at Command to display first few and last few lines of a file (try
seq 30 | (head && tail)for instance).– Stéphane Chazelas
Mar 26 at 20:16
2
I meant that answer. That Q&A has two answers of mine because another Q&A was merged with it (see question history)
– Stéphane Chazelas
Mar 26 at 20:24