What is the difference in using "touch file" and "> file" in creating a new file?

Solution 1:

> is the shell redirection operator. See What's is the difference between ">" and ">>" in shell command? and When should I use < or <() or << and > or >()? It is primarily used to redirect the output of a command to a file. If the file doesn't exist, the shell creates it. If it exists, the shell truncates it (empties it). With just > file, there is no command, so the shell creates a file, but no output is sent to it, so the net effect is the creation of an empty file, or emptying an existing file.

touch is an external command that creates a file, or updates the timestamp, as you already know. With touch, the file contents are not lost, if it exists, unlike with >.

The behaviour of > depends on the shell. In bash, dash, and most shells, > foo will work as you expect. In zsh, by default, > foo works like cat > foo - zsh waits for you type in input.

Solution 2:

Here is an interesting comparison:

$ cat redirect.sh touch.sh sed.sh awk.sh cp.sh truncate.sh tee.sh vi.sh
> redirect.txt
touch touch.txt
sed 'w sed.txt' /dev/null
awk 'BEGIN {printf > "awk.txt"}'
cp /dev/null cp.txt
truncate -s0 truncate.txt
tee tee.txt </dev/null
vi -esc 'wq vi.txt'

Result:

$ strace dash redirect.sh | wc -l
387

$ strace dash touch.sh | wc -l
667

$ strace dash sed.sh | wc -l
698

$ strace dash awk.sh | wc -l
714

$ strace dash cp.sh | wc -l
786

$ strace dash truncate.sh | wc -l
1004

$ strace dash tee.sh | wc -l
1103

$ strace dash vi.sh | wc -l
1472