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Added an example of moving from ls to find.

Matthew O. Persico
2019-04-02 15:45:40 -04:00
parent 823e9f6032
commit 3cd92cd9d4
1 changed files with 43 additions and 2 deletions
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45
SC2012.md

@@ -1,4 +1,4 @@
## Use find instead of ls to better handle non-alphanumeric filenames.
## Use `find` instead of `ls` to better handle non-alphanumeric filenames.
### Problematic code:
@@ -28,7 +28,48 @@ total 0
It shows three seemingly identical filenames, and did you spot the time format change? How it formats and what it redacts can differ between locale settings, `ls` version, and whether output is a tty.
`ls` can usually be substituted for `find` if it's the filenames you're after.
### Tips for replacing `ls` with `find`:
#### Just the filenames, ma'am
`ls` can usually be replaced by `find` if it's just the filenames you're after. Note that if you are using `ls` to get at the contents of a directory, a straight substitution of `find` may not yield the same results as `ls`. Here is an example:
```
$ ls -c1 .snapshot
rnapdev1-svm_4_05am_6every4hours.2019-04-01_1605
rnapdev1-svm_4_05am_6every4hours.2019-04-01_2005
rnapdev1-svm_4_05am_6every4hours.2019-04-02_0005
rnapdev1-svm_4_05am_6every4hours.2019-04-02_0405
rnapdev1-svm_4_05am_6every4hours.2019-04-02_0805
rnapdev1-svm_4_05am_6every4hours.2019-04-02_1205
snapmirror.1501b4aa-3f82-11e8-9c31-00a098cef13d_2147868328.2019-04-01_190000
```
versus
```
$ find .snapshot -maxdepth 1
.snapshot
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0005
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0405
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0805
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-01_1605
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-01_2005
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_1205
.snapshot/snapmirror.1501b4aa-3f82-11e8-9c31-00a098cef13d_2147868328.2019-04-01_190000
```
You can see two differences here. The first is that the `find` output has the full paths to the found files, relative to the current working directory from which `find` was run whereas `ls` only has the filenames. You may have to adjust your code to not add the directory to the filenames as you process them when moving from `ls` to `find`.
The second difference in the two outputs is that the `find` command includes the searched directory as an entry. This can be eliminated by always using a negative name option for the searched directory:
```
$ find .snapshot -maxdepth 1 ! -name .snapshot
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0005
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0405
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_0805
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-01_1605
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-01_2005
.snapshot/rnapdev1-svm_4_05am_6every4hours.2019-04-02_1205
.snapshot/snapmirror.1501b4aa-3f82-11e8-9c31-00a098cef13d_2147868328.2019-04-01_190000
```
#### All the other info
If trying to parse out any other fields, first see whether `stat` (GNU, OS X, FreeBSD) or `find -printf` (GNU) can give you the data you want directly.