New dry-run mode for nfexpire

[MuriloChianfa]

Hey @phaag 👋,

Recently working with nfdump, I notice that sometimes when using the nfexpire tool, we can't be so sure how many files we'll delete using the arguments, so I tried to implement a new option to first make a dry-run, where will be possible to see which files and folders that will be deleted before executing it. Here are some examples:

Environment:

[root@processor: tmp]# ./nfexpire -r /netflow/vs-bgp/ 
Scanning files in /netflow/vs-bgp .. done.
Updating nfcapd bookkeeping records
First:     2026-01-26 05:20:00
Last:      2026-01-30 13:50:00
Lifetime:  376200 = 4.4 days
Numfiles:  1254
Filesize:  2903126016 = 2.7 GB
Max Size:  3865470566 = 3.6 GB
Max Life:  <none>
Watermark: 90%
Status:    OK

dry-run mode:

[root@processor: tmp]# ./nfexpire -e /netflow/vs-bgp/ -s 2.7G -n
DRY-RUN MODE: Simulating expire operation

Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601260520 (size: 1093632 = 1.0 MB)
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601260525 (size: 1040384 = 1016.0 KB)
...manually truncated for demo purposes
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601261820 (size: 3022848 = 2.9 MB)
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601261825 (size: 2994176 = 2.9 MB)

Would expire files:      158
Would expire file size:  296120320 = 282.4 MB
Would expire time range: 47400 = 13.2 hours

DRY-RUN MODE: No files deleted

First:     2026-01-26 05:20:00
Last:      2026-01-30 13:50:00
Lifetime:  376200 = 4.4 days
Numfiles:  1254
Filesize:  2903126016 = 2.7 GB
Max Size:  3865470566 = 3.6 GB
Max Life:  <none>
Watermark: 90%
Status:    OK

executing the expire:

[root@processor: tmp]# ./nfexpire -e /netflow/vs-bgp/ -s 2.7G   
Expired files:      158
Expired file size:  296120320 = 282.4 MB
Expired time range: 47400 = 13.2 hours

First:     2026-01-26 18:30:00
Last:      2026-01-30 13:50:00
Lifetime:  328800 = 3.8 days
Numfiles:  1096
Filesize:  2607005696 = 2.4 GB
Max Size:  2899102924 = 2.7 GB
Max Life:  <none>
Watermark: 90%
Status:    OK

dry-run showing the folder that would be deleted too:

[root@processor: tmp]# ./nfexpire -e /netflow/vs-bgp/ -s 2.3G -n
DRY-RUN MODE: Simulating expire operation

Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601261830 (size: 3055616 = 2.9 MB)
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601261835 (size: 3051520 = 2.9 MB)
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601261840 (size: 2981888 = 2.8 MB)
...manually truncated for demo purposes
Would delete: /netflow/vs-bgp/2026/01/26/nfcapd.202601262355 (size: 4194304 = 4.0 MB)
Would remove directory: /netflow/vs-bgp/2026/01/26
Would delete: /netflow/vs-bgp/2026/01/27/nfcapd.202601270000 (size: 4177920 = 4.0 MB)
Would delete: /netflow/vs-bgp/2026/01/27/nfcapd.202601270005 (size: 4141056 = 3.9 MB)
...manually truncated for demo purposes
Would delete: /netflow/vs-bgp/2026/01/27/nfcapd.202601270540 (size: 880640 = 860.0 KB)
Would delete: /netflow/vs-bgp/2026/01/27/nfcapd.202601270545 (size: 901120 = 880.0 KB)

Would expire files:      136
Would expire file size:  384692224 = 366.9 MB
Would expire time range: 40800 = 11.3 hours

DRY-RUN MODE: No files deleted

First:     2026-01-26 18:30:00
Last:      2026-01-30 13:50:00
Lifetime:  328800 = 3.8 days
Numfiles:  1096
Filesize:  2607005696 = 2.4 GB
Max Size:  2899102924 = 2.7 GB
Max Life:  <none>
Watermark: 90%
Status:    OK

I've updated the manual including the new -n option with some examples:

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Let me know your thoughts for this new feature.

Kind regards,
Murilo Chianfa