notebook/notes/bash/shebang.md

title	TARGET DECK	FILE TAGS	tags
Shebang	Obsidian::STEM	bash	bash

Overview

The shebang (also writting shabang or sha-bang) is a magic character at the start of a script indicating what command should be run when invoking the script directly. It always begins with ASCII characters #!.[^mendel]

%%ANKI Basic What ASCII characters do shebangs start with? Back: #! Reference: Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.

END%%

%%ANKI Basic What class of programs can be specified in a shebang? Back: Interpreters Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. https://www.gnu.org/software/gawk/manual/gawk.pdf

END%%

%%ANKI Basic The OS will parse a shebang into what three parts? Back: #!, the interpreter, and the rest of the line as a single argument. Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. https://www.gnu.org/software/gawk/manual/gawk.pdf

END%%

%%ANKI Basic What gotcha does Robbins highlight with shebang parsing? Back: The remainder of the line following the interpreter is passed as a single argument. Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. https://www.gnu.org/software/gawk/manual/gawk.pdf

END%%

Some systems limit the length of interpreters to just 32 characters. A simple workaround when encountering this limitation is to introduce a symbolic link.

%%ANKI Basic What workaround is used when shebang interpreter names are too long? Back: Introduce a symbolic link. Reference: Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. https://www.gnu.org/software/gawk/manual/gawk.pdf

END%%

References

• Cooper, Mendel. “Advanced Bash-Scripting Guide,” n.d., 916.
• Robbins, Arnold D. “GAWK: Effective AWK Programming,” October 2023. https://www.gnu.org/software/gawk/manual/gawk.pdf