3 ms·

Does cut(1) work for you?

by bbrazil 10y ago

peterburkimsher 10y ago
cut only supports single ASCII characters as delimiters. Reading a value from "<td>2017-01-09 08:30</td>" is harder than it should be. cut needs single-character delimiters, so only splitting on "<" or ">" won't work. sed trips up on the "/", ":", and "-" without proper escaping. This is before even mentioning Unicode. High-level scripting languages handle all of these just fine. I'd much rather have a standard tool and library for this purpose though.
- protomikron 10y ago
 Maybe use awk? $ echo '<td>2017-01-09 08:30</td>' | awk -F'[<>]' '{print $5}' This will give you '08:30'. Unicode seems to be also supported: $ echo 'λf. (λx. f (x x)) (λx. f (x x))' | awk -F'[λ.]' '{print $4}' This prints 'x'. For clarity some other matches: $1: '' $2: 'f' $3: ' (' $4: 'x' ...
 - peterburkimsher 10y ago
 Fine, until the next row doesn't have tags. So the $5 no longer matches where it should. I'm just suggesting easier syntax, and a custom tool. Like dd is for disk copying, instead of cp/gzip/etc. A simple tool that will just work. This is the syntax I'm going for: textBetween("<td>", "</td>") | replace ("", "") | replace ("", "") Maybe with some magic strings, e.g. textBetween(":", "end")
 - protomikron 10y ago
 Yeah you are right, but if the input is more sophisticated I would probably use a scripting language and its full-fledged XML parser. Your replace part is already covered by sed (although I agree with you that the escaping can be awkward).
- lucb1e 10y ago
 There's loads of things you can easily do with tools and I'm sure someone will come up with something, but sometimes it's just easier to use Python: cat dates | python -c 'import sys; for line in sys.stdin: print(line.split("<td>"))' Or PHP php -r 'foreach (explode("\n", file_get_contents("dates")) as $line) { print_r(explode("<td>", $line)); }' Or with Perl or Ruby or whatever floats your boat. While writing this I did think of something though, depending on what you're actually trying to do it might work: cat dates | tr "<>" " " | awk '{print $yourColumnOfInterest}'
 - peterburkimsher 10y ago
 As I say, "High-level scripting languages handle all of these just fine". Back to the article. dd is not a disk writing tool. Everything on UNIX is a disk writing tool. dd has one job, and does it right. Again, I propose a single-purpose text delimiter cutting program. It doesn't need to be a whole scripting language, e.g. awk, perl, python, etc. Just get the text between two strings, and have sensible syntax.

Does cut(1) work for you?

by bbrazil 10y ago

Does cut(1) work for you?

cut only supports single ASCII characters as delimiters. Reading a value from "<td>2017-01-09 08:30</td>" is harder than it should be. cut needs single-character delimiters, so only splitting on "<" or ">" won't work. sed trips up on the "/", ":", and "-" without proper escaping. This is before even mentioning Unicode. High-level scripting languages handle all of these just fine. I'd much rather have a standard tool and library for this purpose though.

protomikron 10y ago
Maybe use awk? $ echo '<td>2017-01-09 08:30</td>' | awk -F'[<>]' '{print $5}' This will give you '08:30'. Unicode seems to be also supported: $ echo 'λf. (λx. f (x x)) (λx. f (x x))' | awk -F'[λ.]' '{print $4}' This prints 'x'. For clarity some other matches: $1: '' $2: 'f' $3: ' (' $4: 'x' ...
- peterburkimsher 10y ago
 Fine, until the next row doesn't have tags. So the $5 no longer matches where it should. I'm just suggesting easier syntax, and a custom tool. Like dd is for disk copying, instead of cp/gzip/etc. A simple tool that will just work. This is the syntax I'm going for: textBetween("<td>", "</td>") | replace ("", "") | replace ("", "") Maybe with some magic strings, e.g. textBetween(":", "end")
 - protomikron 10y ago
 Yeah you are right, but if the input is more sophisticated I would probably use a scripting language and its full-fledged XML parser. Your replace part is already covered by sed (although I agree with you that the escaping can be awkward).
lucb1e 10y ago
There's loads of things you can easily do with tools and I'm sure someone will come up with something, but sometimes it's just easier to use Python: cat dates | python -c 'import sys; for line in sys.stdin: print(line.split("<td>"))' Or PHP php -r 'foreach (explode("\n", file_get_contents("dates")) as $line) { print_r(explode("<td>", $line)); }' Or with Perl or Ruby or whatever floats your boat. While writing this I did think of something though, depending on what you're actually trying to do it might work: cat dates | tr "<>" " " | awk '{print $yourColumnOfInterest}'
- peterburkimsher 10y ago
 As I say, "High-level scripting languages handle all of these just fine". Back to the article. dd is not a disk writing tool. Everything on UNIX is a disk writing tool. dd has one job, and does it right. Again, I propose a single-purpose text delimiter cutting program. It doesn't need to be a whole scripting language, e.g. awk, perl, python, etc. Just get the text between two strings, and have sensible syntax.