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In some cases, when you want to apply a pipeline or a complex command to each file, I find it useful to use `while read`:
```sh
~~find . -type d \~~
~~| while read d; do~~
~~find $d -type f -maxdepth 1 \~~
~~| head -n3;~~
done;
```
Hardened version:
```sh
~~find . -type d -print0 \~~
~~| while IFS= read -r -d '' d; do~~
~~find "$d" -type f -maxdepth 1 -print0 \~~
~~| head -z -n3;~~
done;
```
Portable filenames should only use characters from the portable filename character set <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_282>. But if you need to run your script in filesystems that may be compromised, or use non-portable file names for other reasons, use the hardened version.
Read the corresponding documentation of the features:
- find(1):
- `-print0` <https://www.man7.org/linux/man-pages/man1/find.1.html#EXPRESSION>
- sh(1):
- `IFS=` <https://www.man7.org/linux/man-pages/man1/sh.1p.html#RATIONALE>
- read(1):
- `-r` <https://www.man7.org/linux/man-pages/man1/read.1p.html#OPTIONS>
- `-d ''` <https://stackoverflow.com/questions/9612090/how-to-loop-through-file-names-returned-by-find#comment98776168_9612232>
- head(1):
- `-z` <https://www.man7.org/linux/man-pages/man1/head.1.html#DESCRIPTION>
(The above shows the first 3 files in each directory.)
However, this forces an invocation of the command or pipeline for each path name. In general, xargs(1) is the simplest (and usually fastest) way:
```sh
~~find . -type f \~~
~~| xargs mv -t /tmp;~~
```
Hardened version:
```sh
~~find . -type f -print0 \~~
~~| xargs -0 mv -t /tmp;~~
```
(The above moves all files in `.` to `/tmp`.)
- xargs(1):
- `-0` <https://www.man7.org/linux/man-pages/man1/xargs.1.html#OPTIONS>

In some cases, when you want to apply a pipeline or a complex command to each file, I find it useful to use `while read`:
```sh
find . -type d |
while read d; do
find $d -type f -maxdepth 1 |
head -n3;
done;
```
Hardened version:
```sh
find . -type d -print0 |
while IFS= read -r -d '' d; do
find "$d" -type f -maxdepth 1 -print0 |
head -z -n3;
done;
```
Portable filenames should only use characters from the portable filename character set <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_282>. But if you need to run your script in filesystems that may be compromised, or use non-portable file names for other reasons, use the hardened version.
Read the corresponding documentation of the features:
- find(1):
- `-print0` <https://www.man7.org/linux/man-pages/man1/find.1.html#EXPRESSION>
- sh(1):
- `IFS=` <https://www.man7.org/linux/man-pages/man1/sh.1p.html#RATIONALE>
- read(1):
- `-r` <https://www.man7.org/linux/man-pages/man1/read.1p.html#OPTIONS>
- `-d ''` <https://stackoverflow.com/questions/9612090/how-to-loop-through-file-names-returned-by-find#comment98776168_9612232>
- head(1):
- `-z` <https://www.man7.org/linux/man-pages/man1/head.1.html#DESCRIPTION>
(The above shows the first 3 files in each directory.)
However, this forces an invocation of the command or pipeline for each path name. In general, xargs(1) is the simplest (and usually fastest) way:
```sh
find . -type f |
xargs mv -t /tmp;
```
Hardened version:
```sh
find . -type f -print0 |
xargs -0 mv -t /tmp;
```
(The above moves all files in `.` to `/tmp`.)
- xargs(1):
- `-0` <https://www.man7.org/linux/man-pages/man1/xargs.1.html#OPTIONS>

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