expr match "$string" '.*\($substring\)' #从 $string 的结尾提取$substring, $substring 是正则表达式. expr "$string" : '.*\($substring\)' #从 $string 的结尾提取 $substring, $substring 是正则表达式. 1. 2. 3. 4. 示例: stringZ=abcABC123ABCabc # === echo $(expr match "$stringZ"...
${variable%%pattern} # if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest ${variable/pattern/string} # the longest match to pattern in variable is replaced by string. Only the first match is replaced ${variable//pattern/string}...
After deletion of shortest match from back: bash.string In the first echo statement substring ‘*.’ matches the characters and a dot, and # strips from the front of the string, so it strips the substring “bash.” from the variable called filename. In second echo statement substring ‘....
[student@studentvm1 testdir]$ expr length "We can also find the length of a literal string as well as a variable." 70 关于比较操作符,在我们的脚本中使用了大量的检测两个字符串是否相等(例如,两个字符串是否实际上是同一个字符串)的操作。我使用的是非 POSIX 版本的比较表达式: [student@studentvm...
echo{1..$n}# Works in ksh, but not bash/dash/shecho{1..10}# Works in ksh and bash, but not dash/shecho-n 42# Works in ksh, bash and dash, undefined in shexpr match str regex# Unportable alias for `expr str : regex`trap'exit 42'sigint# Unportable signal speccmd &> file#...
STRING True if string is not empty. 即,test命令使用-z STRING操作符来判断STRING字符串的长度是否为 0。 如果为 0,就是空字符串,会返回 true。 具体写法是test -z STRING,使用[命令则写为[ -z STRING ]。 -n STRING操作符判断STRING字符串的长度是否为 0。
chenxin@yunwei-01:~$ [["$var"=~ th.*message ]] &&echo"Sir. Found that."||echo"Sorry Sir. No match be found."Sir. Found that. 61. ^ 脱字符 脱字符(caret)。 \1. 在正则表达式中,作为一行的行首(beginning-of-line)位置标志符; ...
The string is empty Explanation:In the exercise above,The variable 'input_str' is defined as an empty string. An if statement checks if the length of '$input_str' is zero using the -z test operator. If the string is empty, the script prints "The string is empty" using the "echo" ...
一旦一個變量被定義了,它只能用內建命令 unset來 取消(參見下面 shell 內建命令(SHELL BUILTIN COMMANDS) 章節). 一個變量 variable 可以用這樣的語句形式來賦值: name=[value] 如果沒有給出值 value, 變量就被賦爲空字符串。所有值 values 都經過了波浪線擴展,參數和變量擴展,命令替 換,算術擴展和引用的...
regex() {# Usage: regex "string" "regex"[[$1=~$2]] &&printf'%s\n'"${BASH_REMATCH[1]}"} 用法示例: $# 删除开头的空白字符.$regex' hello''^\s*(.*)'hello$# 验证十六进制颜色.$regex"#FFFFFF"'^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'#FFFFFF$# 验证十六进制颜色(无效...