by H. Fosdick © 2024 RexxInfo.org CC: BY-ND
These charts enumerate equivalences between Rexx and Bash. They're for those who know one of these languages and want to learn the other. (This is not intended as an exercise in "which language is better".)
Click here for PDF version.
| Rexx | Bash | |
|---|---|---|
| Easy to learn, use, and maintain | Yes | No (unfriendly syntax) |
| Very powerful | Yes | Yes |
| Open source | Yes | Yes |
| Portable | Yes | Yes |
| Runs on all platforms | Yes | Yes |
| Runs as the OS Shell | No * | Yes |
| Interfaces to tons of tools | Yes | Yes |
| ANSI or ISO Standard | Yes (ANSI-1996) | Yes (POSIX compliant with extensions) |
| Rexx | Bash | |
|---|---|---|
| Dialects | TRL-2, ANSI, Mainframe, ooRexx, NetRexx | Bash (a superset of the Bourne shell) |
| Unique Usage | * Default scripting language for mainframes and several minor platforms
* Interfaces to all mainframe environments and address spaces |
* Default scripting language for Linux (including on Windows and mainframe Linux systems)
* Sometimes the default for BSD, Oracle Solaris, older Apples, other systems |
| Programming paradigms | Procedural, scripting, functional, object-oriented (ooRexx and NetRexx) | Procedural, scripting, functional |
| OOP: classes, objects, multi-inheritance, polymorphism, encapsulation | In ooRexx and NetRexx | Unsupported |
| User Group | Rexx Language Association | Free Software Foundation |
| Quick Online Lookup | Quick Lookup | DevHints, LinuxTutorials |
| Cheat Sheet (printable PDF) | ANSI Rexx, Mainframe Rexx | LinuxSimply, Cheatography |
| Forum | RexxLA forum | LinuxQuestions.org, Linux.org |
| Further information | RexxInfo.org | Free Software Foundation: GNU Bash |
Covers ANSI-standard "classic Rexx".
| ANSI Rexx | Bash | |
|---|---|---|
| Formatting | Free form | Free form |
| Case-sensitive | No | Yes |
| Comments | Enclose inside /* and */ | Start comment with: # Or, use a Here document for commenting out multiple lines |
| Line Continuation | , (comma) | \ (backslash) |
| Statement Separator | ; (semi-colon) | ; (semi-colon) |
| Code Blocks | Define by do - end | Define by do - done, if - fi, or case - esac |
| Undefined Variables | Allowed. Use SYMBOL to determine if a variable has been defined | Allowed. To error on undefined variables, code: set -u |
| Assignment Operators | = | = += -= *= /= %=
Compound Bitwise: &= |= <<= >>= ^= |
| Arithmetic Operators | + - * / % ** // | + - * / % **
Compound: += -= *= /= %= Evaluate arithmetic expression: $((expression)) Increment/decrement a value: i++ i-- ++i --i |
| Comparison Operators | == \== >> << >>= \<<
<<= \>> = \= <> ><
> < >= \< <= \>
( \ can be replaced with ¬ in any of these) |
Integers: -eq -ne -gt -ge -lt -le
Strings: = == != > >= < <= =~ |
| Logical Operators | & | && \ (prefix) ¬ (prefix) | && || ! (prefix) |
| Concatenation Operators | || Or, concatenate with blank between
Or, concatenate by abuttal (no blank) |
+= Or, use abuttal: VAR3="$VAR1$VAR2" |
| Bitwise Operators | Use built-in functions | & | ^ << >> ~
Compound: &= |= <<= >>= ^= |
| Membership Operators | Unsupported | Unsupported |
| String Parsing | PARSE instruction | Use regular expressions |
| Regular Expressions | Use RexxRE Regular Expressions external Library | Yes |
| Built-in Functions | About 70 functions | None in the traditional sense, designed to issue shell and line commands |
| Data Types | Everything's a string, types are reflected in usage | By default, variables are untyped. Or use "declare" to explicitly type them as: -a, -A, -i, -l, -n, -r, -t, -u, -x |
| Function to Check Data Type | datatype | declare -p |
| Collections of Variables | Use compound variables | One-dimensional arrays: declare -a array_name |
| Associative Arrays | Use compound variables | declare -A array_name |
| Multidimensional Arrays | Use compound variables | Unsupported |
| Stack & Queue Operations | Yes (push, pull, parse pull, queue, queued) | No generalized facility (offers a directory stack with pushd, popd, and dirs) |
| Decimal Arithmetic | Default | Install and use: bc |
| Flow of Control | if, do, select, call, exit, return, iterate, leave, signal, nop | until, while, for, break, continue, return, exit |
| Trace Script Execution | trace (instruction), trace (function) | Use the -x option. Run the script: bash -x
or inside the script: set -x |
| Terminate Process | exit | exit |
| Get User Input | say "Enter your name:" parse pull name | echo -n "Enter your name: " read name |
| Exception Handling | signal | trap |
| Standard Exceptions | novalue, error, failure, halt, notready, syntax, lostdigits | trap covers 64 signal specs (list them by: trap -l) |
| Run an Operating System Command | Just issue the command string (Rexx passes unrecognized strings to the default active environment) | Just issue the command string |
Based on Rexx Programmer's Reference and Bash Reference Manual version 5.2. Thank you to several members of the Rexx LA who gave advice and feedback on this content.
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