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dd: support the [io]flag=nocache option

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Add support for the `iflag=nocache` and `oflag=nocache` to make `dd`
discard the filesystem cache for the processed portion of the input or
output file.
This commit is contained in:
Jeffrey Finkelstein 2023-02-23 22:05:47 -05:00
parent cc2f97ba0d
commit bd18a2a344
4 changed files with 75 additions and 3 deletions
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22
tests/by-util/test_dd.rs
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@ -1536,3 +1536,25 @@ fn test_multiple_processes_reading_stdin() {
.succeeds()
.stdout_only("def\n");
}
/// Test that discarding system file cache fails for stdin.
#[test]
#[cfg(target_os = "linux")]
fn test_nocache_stdin_error() {
new_ucmd!()
.args(&["iflag=nocache", "count=0", "status=noxfer"])
.fails()
.code_is(1)
.stderr_only("dd: failed to discard cache for: 'standard input': Illegal seek\n0+0 records in\n0+0 records out\n");
}
/// Test for discarding system file cache.
#[test]
#[cfg(target_os = "linux")]
fn test_nocache_file() {
let (at, mut ucmd) = at_and_ucmd!();
at.write_bytes("f", b"a".repeat(1 << 20).as_slice());
ucmd.args(&["if=f", "of=/dev/null", "iflag=nocache", "status=noxfer"])
.succeeds()
.stderr_only("2048+0 records in\n2048+0 records out\n");
}