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dev:scripting:start [2008/07/18 06:12] stefanha created |
dev:scripting:start [2009/05/22 13:32] (current) stefanha |
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| - | This page is for brainstorming a scripting language for gPXE. | + | This page is for brainstorming a scripting language for gPXE. Feel free to edit to your heart's delight - everything should be versioned by the wiki anyway! |
| + | |||
| + | === Commands === | ||
| + | The current gPXE shell strips whitespace from a line and splits into an ''argv[]'' array: | ||
| + | <code> | ||
| + | command [arg1 [arg2 [arg3 ...]]] | ||
| + | </code> | ||
| + | |||
| + | === Variables === | ||
| + | Currently, settings like the IP address and boot filename are available as variables. In the future, scripts should be able to create temporary variables as scratch space. | ||
| + | <code> | ||
| + | set net0/ip 192.168.0.1 | ||
| + | set my_ip 10.0.0.15 | ||
| + | show net0/netmask | ||
| + | clear net0/gateway | ||
| + | </code> | ||
| + | |||
| + | Variable expansion is already available in mainline gPXE: | ||
| + | <code> | ||
| + | dhcp ${my_iface} | ||
| + | initrd http://etherboot.org/initrds/${node_id}.bz2 | ||
| + | </code> | ||
| + | |||
| + | "References" could work like this: | ||
| + | <code> | ||
| + | set ref_to_ip net0/ip | ||
| + | show ${ref_to_ip} | ||
| + | => ...value of net0/ip... | ||
| + | </code> | ||
| + | |||
| + | === Arithmetic === | ||
| + | Standard arithmetic operators should work for integral types: | ||
| + | <code> | ||
| + | set i ${(i / 2 + 1) * 2} | ||
| + | </code> | ||
| + | |||
| + | The operators are: ''+'', ''-'', ''*'', ''/'', ''%'', ''('', and '')''. | ||
| + | |||
| + | === String manipulation === | ||
| + | The format string built-in function allows string concatentation and formatting: | ||
| + | <code> | ||
| + | set net0/ip ${fmt("%d.%d.%d.%d", 192, 168, 0, 10 + host_num)} | ||
| + | </code> | ||
| + | |||
| + | === Comparison and logic === | ||
| + | The standard operators for integral and string types (string ordering probably isn't necessary though): | ||
| + | <code> | ||
| + | == != < > <= >= | ||
| + | </code> | ||
| + | |||
| + | They should either evaluate to special boolean values "true"/"false", or we need to define truth rules for all types (e.g. integral types are true if not equal to zero). | ||
| + | |||
| + | === Control flow === | ||
| + | The only control flow statement is the ''if'' statement: | ||
| + | <code> | ||
| + | if <expression> goto <label> | ||
| + | </code> | ||
| + | |||
| + | For example: | ||
| + | <code> | ||
| + | set i 0 | ||
| + | loop: | ||
| + | dhcp net${i} | ||
| + | kernel ${kernel_url} | ||
| + | boot | ||
| + | set i ${i + 1} | ||
| + | if ${i < $iface_count} goto loop | ||
| + | </code> | ||
| + | |||
| + | === Needs discussion === | ||
| + | * We probably need an exit code built-in variable like ''$?'' in POSIX shell. | ||
| + | * Bitwise operators ''|'', ''&'', ''^'', ''~'', ''<<'', and ''>>'' may be needed. | ||
| + | * Focus needs to be on what we can leave out rather than what to add. | ||
| + | * More use cases so we know what users need. | ||
| + | |||
| + | === Links === | ||
| + | * [[http://bellard.org/otcc/|Obfuscated Tiny C Compiler]] | ||
| + | * [[http://www.nicholson.com/rhn/files/dds_basic.c|TINY obfuscated C BASIC interpreter]] | ||
| + | * [[http://www.ittybittycomputers.com/IttyBitty/TinyBasic/TinyBasic.c|TinyBasic]] | ||
| + | * [[http://www.personal.leeds.ac.uk/~bgy1mm/Minibasic/basic.c|Mini BASIC]] | ||
