Various miscellany that doesn't fit anywhere else

# date

Handy for getting the date, but you can also format it and include it the output when renaming things.

```bash
DATE=$(date +%Y%m%d)
```

# diff

You can compare two directories using...

```bash
diff --brief -r dir1/ dir2/
```

Diffing on two different systems

# find

I'm forever forgetting how to use `find` so have written down examples I found from [here](https://www.tecmint.com/35-practical-examples-of-linux-find-command/).

```bash
# Find files of name blah in / (ignores case)
find / -iname blah
# Find files of name blah in / (case sensitive)
find / -name blah
# Find directories of name blah in /home
find /home -type d -name blah
# Find files using glob
find /home -type f -name "*.txt"
# Permissions 777
find / -type f -perm 0777 -print
# Without Permissions 777
find / -type f ! -perm 0777 -print
# File based on user
find /home -user blah
# File based on group
find /home -group blah
# Modified in the last 50 days
find / -mtime 50
# Accessed in the last 50 days
find / -atime 50
# Modified last 50-100 days
find -mtime +50 -mtime -100
# Modified in last hour
find / -mmin -60
# Files based on size
find / -szie +50M -size -100M
```

# rename

Will rename files using an [[bash:sed|sed]] like syntax.  For example to lowercase all file names

```bash
rename 'y/A-Z/a-z/' *
```

# md5 checksum

Generate the md5 (or otherwise) checksum for all files under a given directory

```bash
# md5 sum for all files in the current directory, following symbolic links (-L)
find -L . -type f -exec md5sum '{}' \; > ~/checksum_of_files.md5
```


# rsync

## Specifying port

If you don't have you `~/.ssh/config` set up to define the port for the target then you sometimes have to specify this on the command line call to `rsync`.

```bash
rsync -av  -e 'ssh -p 2222' * target:~/tmp/.
```

## Specific files

Put a list of the files you want to copy in a file and [use](https://stackoverflow.com/questions/16647476/how-to-rsync-only-a-specific-list-of-files) `--from-file=FILE`

```bash
rsync -av --from-file=some_files_to_copy.txt ~/ remote:~/tmp/.
```

# sort

`sort` is a very useful utility, not only does it do what it says on the tin but it can also reduce a list of rows to unique observations with the `-u` flag.

# tar

You can look at the contents of a tar ball without extracting them using...

```bash
tar -ztf some.tar.gz
```


# wc

Counts characters, words and lines, very handy.

```bash
# Count number of files in a directory
ls -l | grep -v '^total' |  wc -l
```

# wget

Useful for downloading web-pages and files.

```bash
# -nd prevents creation of directory hierarchy
# -r recursive download
# -A only get items with specified extension
wget -nd -r -A jpg,jpeg,png,mp3 http://djriko.com/mixmases.htm
```

# Argument list too long

This happens on occasions and there are some ways around it as explained [[https://www.linuxjournal.com/article/6060|here]].