The break Statement The break statement allows you to exit the current loop. It is often used in an if statement that is contained within a while loop, with the condition in the while loop always evaluating to true. This is useful if the number of times the loop is executed depends on input from the user and not some predetermined number. The break statement exits out of the innermost loop in which it is contained. $ cat break.ksh #!/bin/ksh # Script name: break.ksh typeset -i … [Read more...] about How to use “break” and “continue” statements in shell scripts
How to use until loop in Shell Scripts
The until Loop The until loop is very similar to the while loop, except that the until loop executes as long as the command fails. After the command succeeds, the loop exits and execution of the script continues with the statement following the done statement. The syntax for the until loop is: until control_command do statement1 ... statementN done The control_command can be any command that exits with a success or failure status. The statements can be any utility … [Read more...] about How to use until loop in Shell Scripts
“while” Loop Examples in Shell Scripts
The while loop allows you to repeatedly execute a group of statements while a command executes successfully. The syntax for the while loop is: while control_command do statement1 ... statementN done where, control_command can be any command that exits with a success or failure status. The statements in the body of the while loop can be any utility commands, user programs, shell scripts, or shell statements. When a while statement is executed, the … [Read more...] about “while” Loop Examples in Shell Scripts
Understanding MySQL Query Cache
What is MySQL Query Cache MySQL server features Query Cache Feature for a long time. When in use, the query cache stores the text of a SELECT query together with the corresponding result that is sent to a client. If another identical query is received, the server can then retrieve the results from the query cache rather than parsing and executing the same query again. It caches the full result set produced from a SELECT query: Queries executed must be identical. Cache is stored in … [Read more...] about Understanding MySQL Query Cache
How to enable additional scsi logging in CentOS/RHEL
Question: How to turn on scsi extended debug messages? What are the field/flag definitions of scsi_logging_level? Additional scsi logging messages can be enabled by writing to /proc/sys/dev/scsi/logging_level either via use of the echo or preferably the sysctl command. The kernel parameter consists of ten packed fields, each 3 bits in length. Each field can have a value of 0 to 7. The higher the field's value, the more verbose the logging of messages associated with that field type. NOTE: … [Read more...] about How to enable additional scsi logging in CentOS/RHEL
chattr Command Examples to Change File Attributes (Make files immutable)
Files can also have attributes that are expressed in another way than the permissions we have seen so far. An example of this is making a file immutable (a fancy word, which means it cannot be changed). An immutable file still has normal ownership and group and RWX permissions, but it will not allow the user to change it, even if it contains the writable permission. Another characteristic of this is that the file cannot be renamed. In this post, we are going to discuss on how to use chattr … [Read more...] about chattr Command Examples to Change File Attributes (Make files immutable)