One of the most common arithmetic operations when writing Bash scripts is incrementing and decrementing variables. This is most often used in loops as a counter, but it can occur elsewhere in the script as well. Incrementing and Decrementing means adding or subtracting a value (usually 1), ...
COUNTER从0开始,每次循环处理时, COUNTER加1。 #!/bin/sh # whilecount.sh COUNTER=0 # does the counter = 5 ? while [ $COUNTER -lt 5 ] do # add ono to the counter COUNTER=`expr $COUNTER + 1` echo $COUNTER done 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 运行上述脚本,返回数字1到5...
Let’s create a simple shell scriptlet_cmd.shto show how we can increment an integer variable using theletcommand: $ cat let_cmd.sh #!/bin/bash COUNTER=0 printf "Initial value of COUNTER=%d\n" $COUNTER let COUNTER=COUNTER+1 printf "After 'let COUNTER=COUNTER+1', COUNTER=%d\n" $COU...
In this example, we initialize a counterindexat 0. The ‘while’ loop runs as long asindexis less than the length of thefruitsarray (obtained using${#fruits[@]}). Inside the loop, we print out the current fruit, and then increment theindexby 1. Looping with ‘Until’ Loops An ‘until...
Using the += and -= Counter Operators Examples of the use of these operators are as follows: for increment: num=$((num+=1)) ((num+=1)) let "num+=1" for decrement: num=$((num-=1)) ((num-=1)) let "num-=1" Bash example for the+=and-=counter operators in awhileloop: ...
Counter- This will increment the variable value. Each parameter should be separated by asemicolon(;) and should be enclosed indouble bracketsas shown below. for (( variable; condition; counter )) do Command 1 Command 2 Command N done ...
The postfix operator (counter++) returns the current value ofcounterbefore the increment, while the prefix operator (++counter) increments the value before the assignment. Conclusion After reading this tutorial, you should know how to increment and decrement a variable in Bash. Use the supported op...
# Increment the counter ((counter++)) done The following output will appear after executing the above script. Example-7: Use of for loop with command substitute Create a bash file named loop7.bash with the following script to know the use of for loop to read and print the command output...
First, you need to initialize the counter variable as follows: let "errorCounter = 0" Then, issue the line command and capture the return code using the $? variable. If the return code is different than 0, then increment the counter by one (see the statement in bold blue): ...
您不需要比较文件，只需按时间倒序列出并跳过前三个文件。该列表中剩余的任何文件都是您要删除的文件。