mirror of https://github.com/tLDP/LDP
67 lines
1.7 KiB
Bash
67 lines
1.7 KiB
Bash
#!/bin/bash
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# commentblock.sh
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: <<COMMENTBLOCK
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echo "This line will not echo."
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This is a comment line missing the "#" prefix.
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This is another comment line missing the "#" prefix.
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&*@!!++=
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The above line will cause no error message,
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because the Bash interpreter will ignore it.
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COMMENTBLOCK
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echo "Exit value of above \"COMMENTBLOCK\" is $?." # 0
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# No error shown.
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echo
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# The above technique also comes in useful for commenting out
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#+ a block of working code for debugging purposes.
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# This saves having to put a "#" at the beginning of each line,
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#+ then having to go back and delete each "#" later.
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# Note that the use of colon, above, is optional.
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echo "Just before commented-out code block."
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# The lines of code between the double-dashed lines will not execute.
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# ===================================================================
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: <<DEBUGXXX
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for file in *
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do
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cat "$file"
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done
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DEBUGXXX
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# ===================================================================
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echo "Just after commented-out code block."
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exit 0
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######################################################################
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# Note, however, that if a bracketed variable is contained within
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#+ the commented-out code block,
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#+ then this could cause problems.
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# for example:
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#/!/bin/bash
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: <<COMMENTBLOCK
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echo "This line will not echo."
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&*@!!++=
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${foo_bar_bazz?}
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$(rm -rf /tmp/foobar/)
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$(touch my_build_directory/cups/Makefile)
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COMMENTBLOCK
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$ sh commented-bad.sh
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commented-bad.sh: line 3: foo_bar_bazz: parameter null or not set
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# The remedy for this is to strong-quote the 'COMMENTBLOCK' in line 49, above.
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: <<'COMMENTBLOCK'
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# Thank you, Kurt Pfeifle, for pointing this out.
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