I implemented gifcast, a web page for converting asciinema casts to animated GIFs. Here’s the link:
https://dstein64.github.io/gifcast/
The JavaScript source code is available on GitHub:
https://github.com/dstein64/gifcast
The example below was generated with gifcast.
Here is the asciinema cast file used to generate the animated GIF: gifcast.cast
This post contains implementations of echo and printenv in 32-bit x86 assembly for Linux.
echo is a Unix utility that prints its arguments to standard output.
printenv is a Unix utility that prints the environment to standard output.
The core functionality of these programs can be written in a few lines of C, where program arguments and the environment are passed as function arguments to main.
When a process is executed on Linux (or other Unix-like systems), its stack contains pointers to the program arguments and the environment, as shown below.
|--------------------------| Low
0(%esp) | Argument Count | Addresses
|--------------------------|
4(%esp) | Argument Pointers |
| ... |
|--------------------------|
| 0 |
|--------------------------|
| Environment Pointers |
| ... |
|--------------------------|
| 0 |
|--------------------------|
| Additional Data |
| ... | High
|--------------------------| Addresses
This post explains what I’m referring to by color coded bash prompt, why it is useful to have one, and presents an implementation.
By color coded bash prompt, I am referring to the use of colors to represent aspects of the environment running bash. An ordinary bash prompt may display a username and hostname. Color coding can be used to represent whether the user is root, whether the session is running on a local or remote machine, and other aspects of the environment (not covered in this post).
When running multiple terminals at the same time, with some connected to remote machines and/or running as root, color coding makes it easier to keep track of the sessions, and may help prevent inadvertently entering a command as root or on the wrong machine.
I have configured my bash prompt’s colors to be a function of whether I am running as a root or non-root user, and whether I am connected to a local or remote machine. The username is displayed in green for a non-root user and in red for the root user. The hostname is displayed in blue for a local bash session and in cyan for a remote session.
The following image shows the four possible scenarios, 1) on a local machine as a non-root user, 2) on a local machine as root, 3) on a remote machine as a non-root user, and 4) on a remote machine as root.
