在Bash中,while read循环用于从输入流中逐行读取数据,并将每一行赋值给一个变量,然后执行循环体中的命令。串联Bash问题是指在while read循环中如何实现多个命令的串联执行。 要在while read循环中实现多个命令的串联执行,可以使用管道符号|将命令连接起来。管道符号将前一个命令的输出作为后一个命令的输入。 以下是一个示...
linux bash while read循环读管道 在Linux的Bash中，可以使用`while read`循环从管道中读取数据。下面是一个示例脚本：```bash #!/bin/bash sum=0 cat ./whileTest.txt | while read line do line_n=`echo $line|sed 's/(^0-9)//g'`if ( "$line_n" != '' )then echo $line_n sum=$($...
...本教程解释了Bash中while循环的基础知识,以及用于改变循环流的break和continue语句。...Bash while 循环 只要给定条件的计算结果为true,while循环就会使用一组给定的命令执行未知次数。...while循环将一直运行,直到读取最后一行。 当逐行读取文件中的行始终使用read与-r选项,以防止反斜线作为转义字符。...在下面...
自己开发的过程中,我从数据库里读出来一个值,写入某个临时文件,再让脚本做 cat tmp.log |while read line 的时候 readline每次都是少一行, 最后发现,是换行符的问题 从数据库读出的是纯字符,没有换行,需要手动添加一个"\n" 问题解决
read -p "Input something:" STRING done # 方法一: #!/bin/bash # who | grep "hadoop" &> /dev/null RETVAL=$? until [ $RETVAL -eq 0 ];do echo "hadoop is not logged in." sleep 5 who | grep "hadoop" &> /dev/null RETVAL=$? done echo "hadoop is logged in." # 方法二: ...
[Bash Shell 程序设计]当while read 遇上ssh 先看一段简化过的BASH SHELL代码 TODAY=`date +%Y%m%d` SUFFIX="tar" CONF=the_config_file i=0 while read HOST SRCPATH DSTPATH do (( i++ )) if [ "X${HOST:0:1}" = "X#" -o ${#DSTPATH} -eq 0 ]...
#!/bin/bash filename="sample.txt" while read line do echo $line done < "$filename" In the above example, we define the filename as before. The while loop reads the file line by line using the read command, and the '<' character is used to redirect the input from the file. R...
| i'm reading a few variables from a file using while read a b c; do (something) done < filename is there an elegant way to skip a variable (read in an empty value), i.e. if I want a=1 b= c=3, what should I write in the file?
while read LINE do COMMAND done < FILE The same construction in one line (easy to use on the Linux command line): while read LINE; do COMMAND; done < FILE As example lets print all users from the/etc/passwdfile: $ while read LINE; do echo "$LINE" | cut -f1 -d":"; done < ...
#!/bin/bash declare -A map while read line; do arr=($line) [[ ${arr[0]} == tcp ]] && [[ ${arr[4]} =~ :3306 ]] && ((map["${arr[4]}"]++)) done <nowcoder.txt for i in ${!map[@]}; do arr=(${i//:/ }) echo ${map[${i}]}' '${arr[0]} done | sort...