Совет дня:

Условные выражения для строковых переменных в bash

# True if the shell variable varname is set (has been assigned a value).
[[ -v ${varname} ]]

# True if the length of the string is zero.
[[ -z ${string} ]]

# True if the length of the string is non-zero.
[[ -n ${string} ]]

# True if the strings are equal. = should be used with the test command for POSIX conformance. When used with the [[ command, this performs pattern matching as described above (Compound Commands)
[[ ${string1} == ${string2} ]]

# True if the strings are not equal.
[[ ${string1} != ${string2} ]]

# True if string1 sorts before string2 lexicographically.
[[ ${string1} < ${string2} ]]

# True if string1 sorts after string2 lexicographically.
[[ ${string1} > ${string2} ]]

опубликовано в @gitgate

#tips #bash