Managing system resources with awk

In AWK, you can manage system resources by using built-in variables and functions to access system information, and control structures to implement resource management logic. Here are some commonly used techniques for managing system resources with AWK:

– **Built-in variables:** AWK provides several built-in variables that you can use to access system information. Here are some commonly used built-in variables:

– `NF`: The number of fields in the current input line.
– `NR`: The current record number (line number) of the input file.
– `ARGC`: The number of command-line arguments.
– `ARGV`: An array of command-line arguments.

Here is an example of using built-in variables in AWK to manage system resources:

`
# Print the top 5 processes by CPU usage
BEGIN {
printf “%-10s %s\n”, “PID”, “%CPU”
printf “%-10s %s\n”, “—“, “—-”
}
{
if (NR > 1 && $3 > 0) {
processes[$1] = $3
}
}
END {
PROCINFO[“sorted_in”] = “@val_num_desc”
for (pid in processes) {
printf “%-10s %.2f\n”, pid, processes[pid]
if (–count == 0) break
}
}

In this example, we usethe `NF` variable to get the number of fields in the current input line, and the `NR` variable to get the current record number (line number) of the input file. We use the `ARGC` and `ARGV` variables to access command-line arguments.

– **Functions:** AWK provides several functions that you can use to manage system resources. Here are some commonly used functions:

– `system`: Executes a shell command.
– `getline`: Reads the next input line into a variable.
– `close`: Closes a file or pipe.

Here is an example of using functions in AWK to manage system resources:

`
# Monitor the disk usage of a directory
BEGIN {
dir = “/var/log”
cmd = “du -sh ” dir
while ((cmd | getline) > 0) {
print $1 ” used in ” dir
}
close(cmd)
}

In this example, we use the `system` function to execute a shell command that computes the disk usage of a directory (`du -sh`). We use the `getline` function to read the output of the command into a variable (`$0`), and then use the `print` statement to output the disk usage information. We use the `close` function to close the pipe and free system resources.

– **Control structures:** You can use control structures (`if`, `else`, while`, etc.) to implement resource management logic in your AWK scripts. Here is an example of using an `if` statement in AWK to manage system resources:

`
# Kill processes that are using too much CPU
{
if (NR > 1 && $3 > 50) {
cmd = “kill ” $1
system(cmd)
print “Process ” $1 ” killed”
}
}

In this example, we use the `if` statement to check if the third field in the input line (CPU usage) is greater than 50. If so, we use the `system` function to execute a shell command that kills the process with the specified PID (`kill $1`). We use the `print` statement to output a message indicating that the process was killed.

These are just a few examples of the techniques that you can use in AWK to manage system resources. Remember that AWK is a powerful tool for text processing and manipulation, and can be used to implement a wide range of system administration tasks.