URL:
<https://savannah.gnu.org/bugs/?63576>
Summary: Improve find manual with examples and explanations
for -size option
Project: findutils
Submitter: lgtr
Submitted: Mon 26 Dec 2022 01:42:25 PM UTC
Category: documentation
Severity: 3 - Normal
Item Group: None
Status: None
Privacy: Public
Assigned to: None
Originator Name:
Originator Email:
Open/Closed: Open
Release: 4.9.0
Discussion Lock: Any
Fixed Release: None
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Follow-up Comments:
-------------------------------------------------------
Date: Mon 26 Dec 2022 01:42:25 PM UTC By: LGTR <lgtr>
For this manual:
https://www.gnu.org/software/findutils/manual/html_mono/find.html#Size
My suggestion is to improve/clarify the exact operation of the "-size" option
with further examples and explanations, since it's difficult to grasp what it
really means.
Even official GNU documentation like the one for tar wrongly describes how it
operates based on file sizes:
https://www.gnu.org/software/tar/manual/tar.html#files
https://www.gnu.org/software/tar/manual/tar.html#nul
Basically they treat default block size as 1K instead of 512B.
Some examples and explanation could be as follows:
----
*2.6 _-size_ options and parameters*
$ find [path] -size [+-]n[bckwMG]
Options are optional. Parameters are mandatory.
*2.6.1 BLOCK size and block number*
The number parameter for _-size_ represents how many BLOCKS it will be with
the block size given by the letter afterwards, being the default block size
(no letter) of 512-byte (no units given).
If a letter option is present after the number parameter [bckwMG], each BLOCK
will be in size:
* b: 512-byte block
* c: 1-byte block
* w: 2-byte block
* k: Kibibytes (KiB, units of 1024 bytes), 1024-byte block
* M: Mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes), 1048576-byte
block
* G: Gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes),
1073741824-byte block
*2.6.2 Rounding in entire BLOCK size near _-size_ value*
_find -size_ does not search rounding up to byte value always, but to x bytes
according to specified BLOCK after the number parameter (it can be 1 byte if
set like that).
It finds all files nearing its size in a range of the BLOCK size. Also, you
can put a + or - sign in front of the number parameter to search below or
above the rounded BLOCK size, as explanation follows:
* The "-" range modifier option will set the file size up to, including, 1
BLOCK less times the specified number:
$ find . -size -400 -print
Formula is "file-size <= (n-1)*BLOCK".
This means print files up to, including (400-1)*512-byte.
Will print files <= 204288 bytes (up to, including, 204288 bytes, which equals
to 399*512-byte, which equals to 199.5K)
* If no range modifier is set (may equal to ~ or ≈), will set file size
between the range of bigger than 1 BLOCK less the number specified, up to,
including, times BLOCK the number specified:
find . -size 400 -print
Formula is "(n-1)*BLOCK < file-size <= (n)*BLOCK", which is the same as:
"file-size > (n-1)*BLOCK" & "file-size <= (n)*BLOCK"
This means print files bigger than (400-1)*512-byte up to, including
(400)*512-byte.
Will print files > 204288 and <= 204800 bytes.
* The "+" range modifier sets file size to strictly bigger than BLOCK times:
find . -size +400 -print
Formula is "file-size > (n)*BLOCK".
This means print files bigger than (400)*512-byte.
Will print files > 204800 bytes.
*2.6.3 Size ranges*
As this example demonstrates, any file size is covered, if the 3 range
modifiers were to be used being the rest of the parameters equal, so there is
no case where certain file sizes will not be covered leaving a "gap". Each
range modifier covers a set of BLOCKS, and by all three, all sizes are
covered.
If you want to find files without any rounding, use the "c" parameter, so
BLOCK will equal 1 byte (one ASCII character) and will look intuitive to
novice users. Most likely this is the behavior most users expect, since we are
accustomed to bit/byte precision even when using multipliers.
The example would be then, for 400*512-byte:
find . -size -204800c -print
will print files lesser than 204800 bytes.
find . -size 204800c -print
will print files of 204800 bytes.
find . -size +204800c -print
will print files bigger than 204800 bytes.
*2.6.4 Special cases*
Some cases can be difficult to grasp or understand for novice users, specially
because of the way _find_ operates (in block sizes).
If the range modifier is "-" and "n" equals to "1", it will find only files of
size 0 regardless of the letter after the number or BLOCK size:
$ find . -size -1 -print
$ find . -size -1b -print
$ find . -size -1c -print
$ find . -size -1w -print
$ find . -size -1k -print
$ find . -size -1M -print
$ find . -size -1G -print
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