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soc:2009:lynusvaz:notes:scripting_doc:features_added [2009/08/07 09:53] lynusvaz |
soc:2009:lynusvaz:notes:scripting_doc:features_added [2009/08/16 00:19] (current) lynusvaz |
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| - | The features mentioned here are NOT YET part of mainline gPXE, and are still under development. The modified code can be found in my git repository, in the [[http://git.etherboot.org/?p=people/lynusvaz/gpxe.git;a=shortlog;h=refs/heads/offset|offset]] branch. | + | =====Scripting Features===== |
| - | + | The features mentioned here are NOT YET part of mainline gPXE, and are still under development. The modified code can be found in my git repository, in the [[http://git.etherboot.org/?p=people/lynusvaz/gpxe.git;a=shortlog;h=refs/heads/expt|expt]] branch. | |
| - | Scripting features: | + | |
| - Identifiers | - Identifiers | ||
| - Arithmetic evaluator | - Arithmetic evaluator | ||
| - Quoting | - Quoting | ||
| + | - Branches | ||
| - Return code | - Return code | ||
| - | - Branches | ||
| - Loops | - Loops | ||
| - | 1. See the Identifiers section at: [[http://etherboot.org/wiki/commandline]], for the basic syntax of an identifier. The new code allows identifiers to be 'nested', like: | + | ====Identifiers==== |
| + | See the Identifiers section at: [[http://etherboot.org/wiki/commandline]], for the basic syntax of an identifier. The new code allows identifiers to be 'nested', like: | ||
| set i 0 | set i 0 | ||
| echo ${net${i}/ip} | echo ${net${i}/ip} | ||
| Line 18: | Line 18: | ||
| echo ${net$(${i}+1)/ip} | echo ${net$(${i}+1)/ip} | ||
| will print the IP address of the net1 interface (if it exists). | will print the IP address of the net1 interface (if it exists). | ||
| - | Identifiers are expanded by placing them within ${}. | ||
| - | E.g.: | ||
| - | echo $(1 + 2) | ||
| - | set a 15 | ||
| - | echo $(${a} * 3 + 5) | ||
| - | echo $( ${net0/ip} != "" ) | ||
| - | Output: | ||
| - | 3 | ||
| - | 50 | ||
| - | 1 | ||
| - | 2. Arithmetic expressions can be evaluated by placing them within $(). | + | ====Arithmetic Evaluation==== |
| - | The usual C operators (except assignment) are supported with their usual precendence: | + | Arithmetic expressions can be evaluated by placing them within $(). |
| - | Operators, in order of decreasing precedence: | + | The following operators are supported (in order of decreasing precedence): |
| - !, ~ (logical NOT and bitwise negation) | - !, ~ (logical NOT and bitwise negation) | ||
| - *, /, % (multiplication, division, and modulo) | - *, /, % (multiplication, division, and modulo) | ||
| Line 43: | Line 33: | ||
| - && (logical AND) | - && (logical AND) | ||
| - || (logical OR) | - || (logical OR) | ||
| - | The == and != operators also act on strings. | + | The == and != operators also act on strings. Identifiers are expanded by placing them within ${}. |
| + | E.g.: | ||
| + | echo $(1 + 2) | ||
| + | set a 15 | ||
| + | echo $(${a} * 3 + 5) | ||
| + | echo $( ${net0/ip} != "" ) | ||
| + | Output: | ||
| + | 3 | ||
| + | 50 | ||
| + | 1 | ||
| - | 3. Quoting: | + | ====Quoting==== |
| The \ is used as an escape character. The following sequences are recognised: | The \ is used as an escape character. The following sequences are recognised: | ||
| * \<space> Treats the space as part of the command-line argument | * \<space> Treats the space as part of the command-line argument | ||
| Line 51: | Line 50: | ||
| * \<newline> Concatenates the next line to the current line. Both the \ and the newline character are removed | * \<newline> Concatenates the next line to the current line. Both the \ and the newline character are removed | ||
| * \<any other character> Removes the special meaning of the character (if any) | * \<any other character> Removes the special meaning of the character (if any) | ||
| - | + | Within single-quotes, all characters lose their special meaning. Within double-quotes, the \ and $ retain their special meaning. Single- and double-quotes allow you to use a newline character in a command-line argument. | |
| - | Within single-quotes, all characters lose their special meaning. Within double-quotes, the \ and $ retain their special meaning. | + | |
| E.g.: | E.g.: | ||
| - | set message 'Hello World' | + | set message "Hello World" |
| echo '${message} = '${message} | echo '${message} = '${message} | ||
| set message Hello\ \ World | set message Hello\ \ World | ||
| Line 60: | Line 58: | ||
| set message Hello\ World\ \#1 #'Hello World #1' is treated as a single argument | set message Hello\ World\ \#1 #'Hello World #1' is treated as a single argument | ||
| echo ${message} | echo ${message} | ||
| - | echo 'Hello | + | echo 'Hello |
| - | World' | + | World' # Will introduce a newline between Hello and World |
| echo Hello \ | echo Hello \ | ||
| World | World | ||
| Line 71: | Line 69: | ||
| Hello | Hello | ||
| World | World | ||
| + | Hello World | ||
| It's good to see you! | It's good to see you! | ||
| - | 4. The return code of the previous statement can be checked using the ${rc} variable. | + | ====Branches==== |
| - | A value of 0 means that the command completed successfully, while any other value means the command was not successful. | + | |
| - | + | ||
| - | 5. Branches: | + | |
| The keywords if, else and fi are used to branch command execution: | The keywords if, else and fi are used to branch command execution: | ||
| if <condition> | if <condition> | ||
| Line 94: | Line 90: | ||
| <backup statements> #Call this statement sequence B | <backup statements> #Call this statement sequence B | ||
| done | done | ||
| - | The statements in sequence A are executed one by one. If any of them fails, execution branches immediately to sequence B. If all the statements in sequence A are executed successfully, execution skips sequence B. | + | The statements in sequence A are executed one by one. If any of them fails, execution branches immediately to sequence B. If all the statements in sequence A are executed successfully, execution skips sequence B, and continue after the done statement. |
| E.g.: | E.g.: | ||
| - | if $( ${filename} == "" && ${server} != "") | + | if $( ${filename} != "" && ${server} != "") |
| - | echo "No filename" | + | |
| - | else | + | |
| chain tftp://${server}//${filename} | chain tftp://${server}//${filename} | ||
| + | else | ||
| + | echo "No filename" | ||
| fi | fi | ||
| + | will first check that neither filename and server are not empty, before attempting to boot. If either is empty, display an error message. | ||
| try | try | ||
| Line 110: | Line 107: | ||
| echo "Oops: ${rc}" | echo "Oops: ${rc}" | ||
| done | done | ||
| + | will attempt to boot using the given kernel and initrd. If any of the three commands fail, it displays a message. | ||
| - | 6. While and for loops have been added: | + | ====Return Code==== |
| + | The return code of the previous statement can be checked using the ${rc} variable. | ||
| + | A value of 0 means that the command completed successfully, while any other value means the command was not successful. | ||
| + | |||
| + | E.g.: | ||
| + | dhcp net0 | ||
| + | if $( ${rc} != 0 ) | ||
| + | echo "DHCP failed" | ||
| + | else | ||
| + | chain http://etherboot.org/gtest/gtest.gpxe # (Tom's Root Boot disk) | ||
| + | fi | ||
| + | |||
| + | ====Loops==== | ||
| + | You can use while and for loops as: | ||
| while <condition> | while <condition> | ||
| do | do | ||
| Line 134: | Line 145: | ||
| set i $( ${i} + 1 ) | set i $( ${i} + 1 ) | ||
| done | done | ||
| + | will attempt to get a dhcp connection on each valid interface, and if it is successful, boot using a given file. | ||
| - | for i in 0 1 2 3 $(3 + 1) 5 | + | for i in 0 1 2 3 5 $(6*3) |
| do | do | ||
| - | dhcp net${i} | + | echo 'i =' ${i} |
| - | if $(${rc} == 0) | + | |
| - | chain tftp://${server}//${filename} | + | |
| - | fi | + | |
| done | done | ||
| + | displays: | ||
| + | i = 0 | ||
| + | i = 1 | ||
| + | i = 2 | ||
| + | i = 3 | ||
| + | i = 5 | ||
| + | i = 18 | ||
| + | A break statement will exit a loop, and a continue statement will start the next iteration of the loop. | ||
| + | for i in 1 2 3 4 5 6 | ||
| + | do | ||
| + | if $(${i} == 3) | ||
| + | continue | ||
| + | fi | ||
| + | echo 'i =' ${i} | ||
| + | if $(${i} == 4) | ||
| + | break #This will exit the for loop, not just the if branch | ||
| + | fi | ||
| + | done | ||
| + | displays: | ||
| + | i = 1 | ||
| + | i = 2 | ||
| + | i = 4 | ||
