Here, a filename will be given in the first command-line argument at the execution time. If the file exists, then the content of the file will be printed line by line using the loop; otherwise, an error message will be printed. #!/bin/bash # Check the command-line argument value is...
if [ -e $file ]; then echo "File exists" else echo "File does not exists" fi 1. 2. 3. 4. 5. 6. 7. Similarly for example we can use while loop to check if file does not exists. This script will sleep until file does exists. Note bash negator "!" which negates the -e o...
When a list of a string is read byfor-inloop and any string value contains space then the values split into words based on space if the string value is not quoted with a single or double quotation. The following example shows how a list of string values with space can be read byfor-...
for n in a b c d e do while true do if [ $RANDOM -gt 20000 ] then printf . 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...
uniq: 删除文本文件中出现的行列比如: sort file.txt | uniq expr: 进行数学运算Example: add 2 and 3expr 2 "+" 3 find: 搜索文件比如:根据文件名搜索find . -name filename -print tee: 将数据输出到标准输出设备(屏幕) 和文件比如:somecommand | tee outfile ...
uniq: 删除文本文件中出现的行列比如: sort file.txt | uniq expr: 进行数学运算Example: add 2 and 3expr 2 "+" 3 find: 搜索文件比如:根据文件名搜索find . -name filename -print tee: 将数据输出到标准输出设备(屏幕) 和文件比如:somecommand | tee outfile ...
在Linux / UNIX操作系统下,如何使用bash for loop重复执行某些任务? 如何使用for语句设置无限循环? 如何使用三参数进行循环控制表达式? “ for循环”是bash编程语言的语句,它允许重复执行代码。 for循环被归类为迭代语句,即bash脚本中进程的重复。 例如,您可以运行UNIX命令或任务5次,或使用for循环读取和处理文件列表。
您可以在for循环中使用break语句提前退出。您可以使用break从FOR、WHILE或UNTIL循环中退出。for循环中的General break语句 for I in 1 2 3 4 5do statements1 #Executed for all values of ”I”, up to a disaster-condition if any. statements2 if (disaster-condition) then break #Abandon the loop. fi...
First this program will print “Start program”, then the IF statement will check if the conditional expression[[ $1 -eq 4 ]]is true. It will only be true if you provide4as the first argument to the script. If the conditional expression if true then it will execute the code in betwee...
Let's run it in the shell and see, Check if file and directory exist in bash If you want to check whether a file by the nametestexists in/etc/, or a directory by the name ofDocumentsexists in~, we run the following: #!/bin/bash FILE="/home/user/.bashrc" DIR="/etc/" if [...