Images with `imagemagick`

On MAC OSX: brew install imagemagick.

Cheatsheets

Example to convert pdf to png:

convert -density 150 input.pdf -quality 90 output.png

Resize with Number of horizontal pixels:

convert example.png -resize 200 example.png

Resize with Number of vertical pixels:

convert example.png -resize x100 example.png

For example:
```
echo day | sed s/day/night/
```
By default the output is written to stdout. You may redirect this to a new file, or if you want to edit the existing file in place you should use the ‘-i’ flag:
```
sed -e 's/input/output/' my_file > new_file
sed -i -e 's/input/output/' my_file
```

List files:
```
ls
```
List files with details (-l), classified by time (-t), and show the first 12 results (note the use of a pipe |):
```
ls -lt | head -n 12
```
View head of text files: first 10 lines, first 20 lines respectively
```
head file
head -20 file
```
View tail of text files:
```
tail file
tail -20 file
```

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