str - the String to check, may be null Returns: true if the String is empty or null isNotEmpty public static boolean isNotEmpty(String str) Checks if a String is not empty ("") and not null. StringUtils.isNotEmpty(null) = false StringUtils.isNotEmpty("") = false StringUtils.isNotE...
1. Check Empty String 1 2 3 4 5 6 1. 2. 3. 4. 5. 6. if [[ -z "$emptyString" ]]then echo "Empty"else echo "Not Empty"fi 1. Here is a reference material from Stackoverflowhttp://stackoverflow.com/questions/3767267/check-if-file-exists 1 2 3 4 5 6 7 8 ...
-z is the second supported bash string comparison operator used to check if a string is empty or not. The -z operator functions similarly like -n operator. Below is an example: Most importantly, you should add spaces around the square brackets. If there are no spaces, bash will complain ...
systemd是最初由Red Hat Linux团队开发的Linux系统工具。它包括许多功能，包括用于启动和管理系统进程的...
$JAIL set to a non-empty string (1)# $JAIL set to the empty string (2)# $JAIL can be unset (3)###echo "*** Current value of \$JAIL is '$JAIL' ($HINT) ***" ## Determine if a bash variable is empty or not ##if [ -z "${JAIL}" ]; then echo "JAIL is unset ...
# input check: if [ -z "$1" ] ; then error "ERROR: you must specify a file, use -h for help" fi filen="$1" # rename any .1 , .2 etc file: for n in 9 8 7 6 5 4 3 2 1; do if [ -f "$filen.$n" ]; then ...
A null or empty ("") String will return false. StringUtils.contains(null, *) = false StringUtils.contains("", *) = false StringUtils.contains("abc", 'a') = true StringUtils.contains("abc", 'z') = false Parameters: str - the String to check, may be null ...
Comparison operators are used in bash to compare two strings to check if they are equal or not. Here, we will list some comparison operators including, string, and integer operators. Integer Operators Operators Explanation -eq is equal to -ne is not equal to -gt is greater than -ge is gr...
# input check: if [ -z "$1" ] ; then error "ERROR: you must specify a file, use -h for help" fi filen="$1" # rename any .1 , .2 etc file: for n in 9 8 7 6 5 4 3 2 1; do if [ -f "$filen.$n" ]; then ...
the variable X is not the empty string 为何?这是因为shell将$X展开为空字符串,表达式[-n]返回真值(因为改表达式没有提供参数)。再看这个脚本: 1 2 3 4 5 #!/bin/bash X="" if[ -n"$X"];then# -n 用来检查变量是否非空 echo"the variable X is not the empty string" ...