Test
1
2
3
| test EXPRESSION
[ EXPRESSION ]
[[ EXPRESSION ]]
|
If you want your script to be portable, you should prefer using the old test [ command, which is available on all POSIX shells. The new upgraded version of the test command [[ (double brackets) is supported on most modern systems using Bash, Zsh, and Ksh as a default shell.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
| FILE=/etc/resolv.conf
if test -f "$FILE"; then
echo "$FILE exists."
fi
FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
echo "$FILE exists."
fi
FILE=/etc/resolv.conf
if [[ -f "$FILE" ]]; then
echo "$FILE exists."
fi
|
1
2
3
| test -f /etc/resolv.conf && echo "$FILE exists."
[ -f /etc/resolv.conf ] && echo "$FILE exists."
[[ -f /etc/resolv.conf ]] && echo "$FILE exists."
|
check if file does not exist
1
2
3
4
| FILE=/etc/docker
if [ ! -f "$FILE" ]; then
echo "$FILE does not exist."
fi
|
1
| [ ! -f /etc/docker ] && echo "$FILE does not exist."
|
check if directory exist
1
2
3
4
| FILE=/etc/docker
if [ -d "$FILE" ]; then
echo "$FILE is a directory."
fi
|
1
| [ -d /etc/docker ] && echo "$FILE is a directory."
|
check if multiple file exists
Instead of using complicated nested if/else constructs you can use -a (or && with [[) to test if multiple files exist:
1
2
3
| if [ -f /etc/resolv.conf -a -f /etc/hosts ]; then
echo "Both files exist."
fi
|
1
2
3
| if [[ -f /etc/resolv.conf && -f /etc/hosts ]]; then
echo "Both files exist."
fi
|
1
| [ -f /etc/resolv.conf -a -f /etc/hosts ] && echo "Both files exist."
|
1
| [[ -f /etc/resolv.conf && -f /etc/hosts ]] && echo "Both files exist."
|
file test operators
…
