Displaying Memory Usage in Bash Scripts on Linux

To display memory usage in a bash script, you can make use of various Linux commands and utilities. One such command is free, which provides information about the system's memory usage. Here's an example of how you can use free within a bash script to display memory usage:

#!/bin/bash

# Get memory usage
memory=$(free -m | awk 'NR==2{printf "%.2f%%", $3*100/$2 }')

# Print memory usage
echo "Memory Usage: $memory"

In this example, the free command is used to retrieve memory information. The output of free is then piped to awk, which extracts the memory usage percentage. Finally, the memory usage is printed using the echo command.

The Top Command

To check memory usage in Linux, you can make use of various commands and utilities. One commonly used command is top, which provides real-time information about system resources, including memory usage. Here's an example of how you can use top to check memory usage in Linux:

top -n 1 | grep "KiB Mem"

This command will display the current memory usage in kilobytes. You can modify the command to display memory usage in different units, such as megabytes (MB) or gigabytes (GB), by using appropriate flags or conversion factors.

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The Vmstat Command

In addition to top, Linux provides several other commands to check memory usage. One such command is vmstat, which provides information about virtual memory statistics. Here's an example of how you can use vmstat to check memory usage in Linux:

vmstat -s

This command will display detailed information about memory usage, including total memory, free memory, used memory, and more. You can further customize the output by using different flags or options with the vmstat command.

The Sar Command

Monitoring memory usage is crucial for ensuring optimal system performance. In a bash script, you can use tools like sar (System Activity Reporter) to monitor memory usage over time. Here's an example of how you can use sar to monitor memory usage in Linux:

sar -r 1 10

This command will display memory usage statistics every second for a duration of 10 seconds. You can adjust the duration and frequency of monitoring as per your requirements. The output of sar includes information like free memory, used memory, buffers, cache, and more.

The Ps Command

To show memory usage in a bash script, you can use the ps command to retrieve information about processes and their memory usage. Here's an example of how you can use ps to show memory usage in Linux:

#!/bin/bash

# Get memory usage of a specific process
pid=$(pgrep -f "your_process_name")
memory=$(ps -p $pid -o %mem)

# Print memory usage
echo "Memory Usage: $memory%"

In this example, the pgrep command is used to retrieve the process ID (pid) of a specific process using its name. The ps command is then used to retrieve the memory usage (%mem) of the process identified by the pid. Finally, the memory usage is printed using the echo command.

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Combining multiple Commands and Utilities

To get memory usage in a bash script, you can combine multiple commands and utilities to extract the desired information. Here's an example of a bash script that gets memory usage in Linux:

#!/bin/bash

# Get total memory
total_memory=$(grep "MemTotal" /proc/meminfo | awk '{print $2}')

# Get available memory
available_memory=$(grep "MemAvailable" /proc/meminfo | awk '{print $2}')

# Calculate used memory
used_memory=$((total_memory - available_memory))

# Calculate memory usage percentage
memory_usage=$(awk "BEGIN {printf \"%.2f\", ($used_memory / $total_memory) * 100}")

# Print memory usage
echo "Memory Usage: $memory_usage%"

In this example, the script uses grep and awk to extract the total memory and available memory from the /proc/meminfo file. It then calculates the used memory by subtracting the available memory from the total memory. Finally, it calculates the memory usage percentage and prints the result.

Summary of the Methods to Get Memory Usage

There are multiple methods to get memory usage in a bash script in Linux. Some of the commonly used methods include using commands like free, top, vmstat, and parsing the /proc/meminfo file. Here are a few examples:

Method 1: Using free command

#!/bin/bash

# Get memory usage
memory_usage=$(free -m | awk 'NR==2{printf "%.2f%%", $3*100/$2 }')

# Print memory usage
echo "Memory Usage: $memory_usage"

Method 2: Using top command

#!/bin/bash

# Get memory usage
memory_usage=$(top -b -n 1 | grep "KiB Mem" | awk '{print $8}')

# Print memory usage
echo "Memory Usage: $memory_usage"

Method 3: Using vmstat command

#!/bin/bash

# Get memory usage
memory_usage=$(vmstat -s | grep "total memory" | awk '{printf "%.2f%%", ($1-$2)*100/$1}')

# Print memory usage
echo "Memory Usage: $memory_usage"

Method 4: Parsing /proc/meminfo file

#!/bin/bash

# Get total memory
total_memory=$(grep "MemTotal" /proc/meminfo | awk '{print $2}')

# Get available memory
available_memory=$(grep "MemAvailable" /proc/meminfo | awk '{print $2}')

# Calculate used memory
used_memory=$((total_memory - available_memory))

# Calculate memory usage percentage
memory_usage=$(awk "BEGIN {printf \"%.2f\", ($used_memory / $total_memory) * 100}")

# Print memory usage
echo "Memory Usage: $memory_usage%"

These methods provide different ways to retrieve memory usage in a bash script. You can choose the method that best suits your requirements and incorporate it into your scripts accordingly.

Additional Resources

- Can I view memory usage in a bash script?