How to use the command stdbuf (with examples)
The stdbuf command is used to run a command with modified buffering operations for its standard streams. It allows you to change the buffering behavior of the standard input (stdin), standard output (stdout), and standard error (stderr) streams.
Use case 1: Change stdin buffer size to 512 KiB
Code:
stdbuf --input=512K command
Motivation: When running a command that requires reading a large input from stdin, such as processing a large file or receiving a large amount of data over a network, it may be beneficial to increase the buffer size of stdin to improve performance and avoid system limitations.
Explanation: In this use case, the --input option is used to specify the buffer size for stdin. The size is specified in bytes, and the suffix K represents kilobytes. In the example code, 512K sets the buffer size to 512 kilobytes.
Example output: The specified command will be executed with a stdin buffer size of 512 kilobytes, allowing for more efficient reading of large input data.
Use case 2: Change stdout buffer to line-buffered
Code:
stdbuf --output=L command
Motivation: By default, the standard output (stdout) stream is usually fully buffered, meaning that the data is written to the output only when the buffer is full or when the program terminates. However, there may be situations where you want each line of output to be immediately displayed without waiting for the buffer to fill up.
Explanation: In this use case, the --output option is used to set the buffering mode for stdout. The L argument specifies line buffering, meaning that the output will be flushed after each line of data is written.
Example output: When executing the specified command, the standard output will be line-buffered, resulting in each line of output being immediately displayed without buffering.
Use case 3: Change stderr buffer to unbuffered
Code:
stdbuf --error=0 command
Motivation: When using the standard error (stderr) stream for logging error messages or diagnostic output, it is useful to have the data displayed immediately without buffering. This ensures that important information is not delayed when troubleshooting issues.
Explanation: In this use case, the --error option is used to set the buffering mode for stderr. The 0 argument represents unbuffered mode, which means that the data written to stderr will be immediately displayed without any buffering.
Example output: When running the specified command, the standard error output will be unbuffered, ensuring that any error messages or diagnostic output are displayed immediately without buffering.
Conclusion:
The stdbuf command provides a flexible way to modify buffering operations for standard streams. The use cases described above demonstrate how to change the buffering behavior of stdin, stdout, and stderr to enhance performance, control output visibility, and ensure immediate display of important information.
