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Shell script interpreters like bash do. You can change a bash script while it's running (append, or truncate and re-write) and it'll keep going from the same of

by ploxiln 11y ago

Shell script interpreters like bash do. You can change a bash script while it's running (append, or truncate and re-write) and it'll keep going from the same offset. But then again, shell script is in a different class of language I'd say. #!/bin/bash COUNTER=0 addmore() { echo hi $COUNTER ((COUNTER++)) echo "addmore" >>$0 sleep 1 } addmore

deleted 11y ago
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kazinator 11y ago
Bash reads code from a stream, and doesn't read the entire stream before executing the code. However, the stream pointer isn't its instruction pointer in the script. A backwards branch (such as the end of a while loop, or a call to a function defined earlier) does not rewind the stream to that piece of text. > But then again, shell script is in a different class of language I'd say. Not much different in this regard from how, say, Common Lisp (load "file.lisp") processes the top-level forms in the file. (defvar *counter* 0) (defun addmore () (format t "hi ~s~%" (incf *counter*)) (with-open-file (f "addmore.lisp" :direction :output :if-exists :append) (write-line "(addmore)" f))) $ clisp addmore.lisp hi 1 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @8> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 2 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @9> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 3 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @10> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 4 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @11> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 5

by ploxiln 11y ago

deleted 11y ago

[deleted]

kazinator 11y ago

Bash reads code from a stream, and doesn't read the entire stream before executing the code. However, the stream pointer isn't its instruction pointer in the script. A backwards branch (such as the end of a while loop, or a call to a function defined earlier) does not rewind the stream to that piece of text. > But then again, shell script is in a different class of language I'd say. Not much different in this regard from how, say, Common Lisp (load "file.lisp") processes the top-level forms in the file. (defvar *counter* 0) (defun addmore () (format t "hi ~s~%" (incf *counter*)) (with-open-file (f "addmore.lisp" :direction :output :if-exists :append) (write-line "(addmore)" f))) $ clisp addmore.lisp hi 1 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @8> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 2 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @9> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 3 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @10> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 4 WARNING: OPEN: #<INPUT BUFFERED FILE-STREAM CHARACTER #P"addmore.lisp" @11> already points to file "/home/kaz/test/addmore.lisp", opening the file again for :OUTPUT may produce unexpected results Open the file anyway hi 5