printf "Enter a number between 10 and 20 inclusive: " read number if (( number < 10 )) then printf "%d is too low\n" "$number" >&2 exit 1 elif (( number > 20 )) then printf "%d is too high\n" "$number" >&2 exit 1 else printf "You entered %d\n" "$number" fi 注...
16. $ 美元符-变量/行末 美元符号(Variable substitution[Dollar sign])。 \1. 作为变量的前导符,用作变量替换,即引用一个变量的内容,比如:echo $PATH; \2. 在正则表达式中被定义为行末(End of line)。 17. ${}-变量 参数替换(Variable substitution)。 用于在字符串中表示变量。 17. ${!#} ${@...
You can assign data to a variable using the equals sign (=). The data you store in a variable can either be a string or a number. Let’s create a variable now on the command line: chapter_number=5 The variable name is on the left hand side of the equals sign, and the data whic...
tail –1 “$1” --- tail 命令可用于查看文件的内容, tail –1 somefile.txt 会把somefile.txt的最后一行打印在屏幕上。 if [[ -n $1 ]]; --- [[ 可以理解为更高级更现代的[, 即test命令。这里的语法对于用惯了高级语言的程序员会看起来很不习惯,感觉像if的条件里的比较少了一个操作数一样。...
If the current cursor position is at the end of the current command, the value of this variable equals ${#COMP_LINE}. This variable is available only in shell functions and external commands invoked by the programmable completion facilities (see the section "Programmable Completion" below). ...
In this case, the expression is slightly different, instead of typing true or false, thestdoutvariable is printed using$?. Check if strings are not equals The!=operator checks if String1 is not equal to String2. If the two strings are not equal, then it returns 0. If two strings are...
set -- $variable 1 if [ $file1 -ot $file2 ] then 3 echo "File $file1 is older than $file2." 4 fi 5 6 if [ "$a" -eq "$b" ] 7 then 8 echo "$a is equal to $b." 9 fi 10 11 if "$c" -eq 24 -a "$d" -eq 47 ] 12 ...
11 echo "$decimal equals $octal" 12 else 13 echo "$decimal is not equal to $octal" # 15 is not equal to 017 14 fi # Doesn't evaluate within [ single brackets ]! 17 if [[ "$decimal" -eq "$octal" ]] 18 then 19 echo "$decimal equals $octal" # 15 equals 017 ...
How to find if a number is odd or even in bash? How to iterate over a bash array? How to loop over each line of a file? How to iterate over a list of files? How to use numbers with leading zeros in a bash loop? How to iterate over a range of numbers defined by variables?
making them a good choice for basic array looping. ‘While’ and ‘until’ loops offer more control over the loop condition, which can be useful in more complex scenarios. However, they require you to manually manage a counter variable, which can lead to off-by-one errors if you’re not...