while循环最常见的用法之一是逐行读取文件,数据流或变量。 在下面的示例中,while循环将/etc/passwd逐行读取文件并打印每一行。 file=/etc/passwd while read -r line; do echo $line done < "$file" 我们使用输入重定向(< "$file")将文件传递给read控制循环的命令,而不是使用条件控制while循环。while循环将一...
此方法使用的内存少于mapfile方法,并在bash3中工作,但对于较大的文件,它的速度较慢。 lines_loop() { # Usage: lines_loop "file" count=0 while IFS= read -r _; do ((count++)) done < "$1" printf '%s\n' "$count" } 用法示例: $ lines ~/.bashrc 48 $ lines_loop ~/.bashrc 48 计算...
So a while loop looks like this:while [[ condition ]] do # statements doneJust like in the case of the for loop, if we want to write do and condition in the same line, then we must use a semicolon before do.A working example might look like this:...
While the ‘foreach’ loop (expressed as a ‘for’ loop in Bash) is a powerful tool for iterating over items, it’s not the only method available. Let’s explore some alternative approaches, namely the ‘while’ and ‘until’ loops. The ‘While’ Loop The ‘while’ loop performs a s...
By using this approach, while being an unlikely use case, you can also debug Bash commands from the command line using the -c option. [me@linux ~]$ y=9 [me@linux ~]$ TRACE=1 BASH_ENV=my-debug-env bash -c "x=1; y=$y; echo \$((x+y))" Run TRACE mode [ DEBUG ]| BASH...
while-infinite-loop.sh #!/bin/bash while : do echo 'never stop' done while 语句可以写为一行,用分号隔开。大多数 bash 语句可以写为一行,但是可读性不好。 while-in-one-line.sh #!/bin/bash count=0 while [ "$count" -lt 5 ]; do echo $count; ((count++)); done 单中括号和双中括号区...
Using a "do while" loop in bash scripting is simple. Here, ‘-le’ keywords indicate the "less than or equal" sign of a normal programming language. The following script will run until the variable's value is greater than five. #!/bin/bash echo "Do while loop example" a=1 while [...
lines_loop() {# Usage: lines_loop "file"count=0whileIFS=read-r _;do((count++))done<"$1"printf'%s\n'"$count"} 用法示例: $lines ~/.bashrc48$lines_loop ~/.bashrc48 计算目录中的文件或目录 这是通过将glob的输出传递给函数然后计算参数的数量来实现的。
The * notation will return all the elements of the array as a single word result while the @ notation will return a value for each element of the Bash array as a separate word. This becomes clear when performing a for loop on such a variable....
break 2 ## break out of both while and for loops elif [ $RANDOM -lt 10000 ] then printf '"' break ## break out of the while loop fi done done echo 继续 在循环内部, continue命令通过传递任何剩余命令,立即开始循环的新迭代: for n in {1..9} ## See Brace expansion in Chapter 4 ...