Exploring the 'size' Command in Linux (with examples)

The size command in Linux is a utility that provides valuable information about the sizes of various sections inside binary files. It is commonly used to analyze object files, shared library files, and executable files. By revealing the memory footprint of these sections, the command aids developers and engineers in optimizing file sizes and diagnosing size-related issues in the binary files.

Use case 1: Display the size of sections in a given object or executable file

Code:

size path/to/file

Motivation:

Understanding the memory distribution of a binary file is crucial for developers, especially when optimizing applications for constrained environments like embedded systems. This basic usage of the size command provides a quick summary of how memory is allocated among the different sections of a file, which can help developers identify sections that may require optimization or analysis.

Explanation:

• size: Invokes the command to determine the sizes of sections within a binary file.
• path/to/file: Specifies the path to the object or executable file that needs inspection.

Example output:

   text    data     bss     dec     hex filename
  23103    2345    1024   26472    6788 path/to/file

In this example, the output lists the sizes of text, data, and bss sections, along with their total size in both decimal and hexadecimal formats. This allows you to understand how much memory each section is consuming.

Use case 2: Display the size of sections in a given object or executable file in [o]ctal

Code:

size -o path/to/file

Motivation:

Displaying sizes in octal format can be particularly beneficial for developers who are accustomed to working with permission bits or contexts where octal representation is preferred, such as in certain legacy systems or specific debugging scenarios. This use case assists in aligning the size output with the octal numeral system, which may stylistically or functionally match other elements of the workflow.

Explanation:

• size: Initiates the command.
• -o or --radix=8: Tells the command to display the section sizes in octal form by altering the numeral system base to 8.
• path/to/file: Specifies the file to analyze.

Example output:

   text    data     bss     dec     hex filename
  055507  004431  002000  063150  0f678 path/to/file

Here, the section sizes are displayed in octal form, highlighting how they would appear in this numeral system.

Use case 3: Display the size of sections in a given object or executable file in [d]ecimal

Code:

size -d path/to/file

Motivation:

While decimal format is the default view, this option explicitly requests it, ensuring clarity. Additionally, it serves as a useful switch for users who routinely work in alternative bases but need to switch back to the more universally understood decimal representations for the sake of documentation or comparison.

Explanation:

• size: Calls the command to determine the file section sizes.
• -d or --radix=10: Sets the output format to decimal, using base 10 for size display.
• path/to/file: The location of the file being inspected.

Example output:

   text    data     bss     dec     hex filename
  23103    2345    1024   26472    6788 path/to/file

The sizes remain in decimal form, aligning with everyday numerical use.

Use case 4: Display the size of sections in a given object or executable file in he[x]adecimal

Code:

size -x path/to/file

Motivation:

Using hexadecimal representation can be extremely helpful for developers working closely with memory addresses, as this numeral system is standard in displaying such addresses. It integrates well with other hexadecimal-based operations and readings that developers encounter in tasks like debugging, address mapping, or low-level programming.

Explanation:

• size: Triggers the command to process the file section sizes.
• -x or --radix=16: Commands the output to be in hexadecimal, using base 16, which matches hexadecimal conventions.
• path/to/file: Indicates the file subjected to the analysis.

Example output:

   text    data     bss     dec     hex filename
  0x5a1f  0x929   0x400  0x6778  0x6788 path/to/file

Here, the sizes are presented in hexadecimal, offering clarity for hexadecimal-based systems and applications.

Conclusion:

The size command is a versatile tool that gives insight into the memory allocation of object, library, and executable files. By leveraging its ability to represent section sizes in various numeral systems, developers can customize their analysis to best fit the given context, whether it’s aligning with legacy octal systems, standard decimal representations, or hexadecimal outputs for low-level system work.