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head: printing all-but-last-n-lines discrepancy with GNU #7472

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karlmcdowall opened this issue Mar 17, 2025 · 0 comments · May be fixed by #7484
Open

head: printing all-but-last-n-lines discrepancy with GNU #7472

karlmcdowall opened this issue Mar 17, 2025 · 0 comments · May be fixed by #7484
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@karlmcdowall
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karlmcdowall commented Mar 17, 2025 •
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If the last line of a large file doesn't end with a newline then we get a discrepancy between GNU and Rust implementations.
Steps to reproduce...
1 - make a large file without a line ending...
$ seq 70000 | head -c -1 >seq_70000

2 - Compare GNU with Rust
GNU...

$head -n -1 seq_70000
...
69998
69999

Rust

$./target/debug/head -n -1 seq_70000
...
69997
69998

Issue only exists for large files, small files are handled fine.

I'm planning to fix this.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
4786579 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
373d75b 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
62e2c48 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
2c58ac6 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
62eebd9 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
@karlmcdowall karlmcdowall linked a pull request Mar 18, 2025 that will close this issue
Open
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
59bc44e 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 18, 2025
@karlmcdowall
head: fix bug with non-terminated files.
6131a30 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
karlmcdowall added a commit to karlmcdowall/coreutils that referenced this issue Mar 19, 2025
@karlmcdowall
head: fix bug with non-terminated files.
ee429f8 
Fixes issue uutils#7472.
Update to head app when printing all-but-last-n-lines of a file.
Code now checks if the last line of the input file is missing a terminating
newline character, and if so prints an extra line.
This aligns with GNU-head behavior.
Also improved performance of this usecase by using an optimized iterator
(memchr-iter) for searching through the input file.
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head: fix bug with non-terminated files. karlmcdowall/coreutils
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