The Bash Hackers Wiki, Hacker News

This wiki is intended to hold documentation of any kind about GNU Bash. The main motivation was to provide human-readable documentation and information so users aren’t forced to read every bit of the Bash manpage – which can be difficult to understand. However, the docs here are not meant as a newbie tutorial.

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Scripting and general information

Bash syntax and operations

Expansions and substitutions

Builtin Commands

This is a selection of builtin commands and command-like keywords, loosely arranged by their common uses. These are provided directly by the shell, rather than invoked as standalone external commands.

)

Declaration commands Commands that set and query attributes / types, and manipulate simple datastructures. (Alt)

Type

declare Display or set shell variables or functions along with attributes. (typesets)


 builtin  
 (export Display or set shell variables, also giving them the export attribute. 
 
 (typeset -x) (
) (special builtin 
 (eval (Evaluate arguments as shell code.  - 

 special builtin 

 (local ) Declare variables as having function local scope.  -  
 builtin  
 readonly Mark variables or functions as read-only.   (typeset -r) special builtin  
 (unset 
 Unset variables and functions. - special builtin  
 (shift ) (Shift positional parameters) - special builtin 
 I / O 
 (Commands for reading / parsing input, or producing / formatting output of standard streams.) (Alt 
) (Type) 
 (coproc 
 Co-processes: Run a command in the background with pipes for reading / writing its standard streams.  
 -  keyword  
 
 (echo ) (Create output from arguments.) -  
 builtin  
 (mapfile ) Read lines of input into an array. 
 (readarray) (builtin) 
 printf (advanced) echo . ” 

 - 
 (builtin) 
 (read ) Read input into variables or arrays, or split strings into fields using delimiters.  (builtin) 
 Configuration and Debugging 
 Commands that modify shell behavior, change special options, assist in debugging. Alt  Type 
 (caller ) (Identify / print execution frames.) 
 
 builtin  
 set  (Set the positional parameters and / or set options that affect shell behavior.) 

 -  (special builtin) 
 
 (shopt )  set / get some bash-specific shell options. - (builtin)  


  (Control flow and data processing 
 Commands that operate on data and / or affect control flow. (Alt 
 Type  colon   
 "true" null command.  (true) special builtin 
 (dot) Source external files.  (source) special builtin 
 (false)  Fail at doing nothing.  - 
 builtin 
 
 (continue / break continue with or break out of loops.  - 
 special builtin 
 let Arithmetic evaluation simple command.  - 
 builtin 
 
 (return) Return from a function with a specified exit status.  - 
 special builtin 
 ( (The classic) (test) simple command.  (test) builtin 
 
 Process and Job control 
 Commands related to jobs, signals, process groups, subshells. 
 (Alt ) (Type 

 (exec) Replace the current shell process or set redirections.  - 
 special builtin 
 (exit) 
 Exit the shell.  - 
 special builtin 
 kill Send a signal to specified process (es) - (builtin) 
 trap Set signal handlers or output the current handlers.  - 
 special builtin 
 (times  Display process times.  - 
 special builtin 
 wait Wait for background jobs and asynchronous lists.  - 
 builtin 

 Alt  ()  

  previous alphabetical version 

 ) 
 AG)  caller  (identify / print execution frames (Bash builtin) 
 IN 




 mark variables or functions as read-only (Bash builtin) 
 (UZ) 


 (coproc 
 Co-processes (Bash keyword) 
 
 declare display or set shell variables or functions along with attributes (Bash builtin, synonym: typeset  
 (exec) replace the shell, set redirections (Bash builtin) 


 let arithmetic evaluation - an old fashioned way (Bash builtin) 
 
 (mapfile ) Mapping lines of input to an array, also named readarray  builtin)   

  OT  printf  
 (advanced (echo) "(Bash builtin)  
 (read ) getting input from  stdin (Bash builtin) 
 readonly 

 
 set  control positional parameters and shell behavior (Bash builtin)  
 (shopt )  set / get shell options (Bash builtin)  
 (test) (the classic) (test) command (Bash builtin) 

 (unset 
 unset variables and functions (Bash builtin)   

 A list of expressions, words, and their meanings is here . 

 Official Bash links (Recommended Shell resources) (Documentation / Reference) Assorted interesting links 
 Bash Libraries (needs review)  


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