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...
; done <myfile #If only one word a line, simply for line in $(cat myfile); do echo $line; read -n1; done #Loop through an array for i in "${arrayName[@]}"; do echo $i; done While loop, # Column subtraction of a file (e.g. a 3 columns file) while read a b c; ...
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...
Inquiry: I need assistance with reading a specific column using a while loop. I have a file with multiple columns and I want to iterate through a particular column. The iteration provides the accurate information. However, when I execute the script, it halts at the first line. It just sto...
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:...
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 [...
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....
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...
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 ...
Running for loop from bash shell command line: $ for f in $( ls /var/ ); do echo $f; done 1. 2. 3. 4. 5. 6. 7. 8. 12.2. Bash while loop #!/bin/bashCOUNT=6 # bash while loop while [ $COUNT -gt 0 ]; do echo Value of count is: $COUNT ...