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howtos:general_admin:cli_constructs_and_useful_info [2012/10/21 09:12 (UTC)] htexmexh [Quoting] |
howtos:general_admin:cli_constructs_and_useful_info [2013/04/02 15:19 (UTC)] (current) htexmexh [Constructs] |
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| Line 9: | Line 9: | ||
| ls -1 /var/log/packages | rev | cut -d - -f 1-3 --complement | rev | ls -1 /var/log/packages | rev | cut -d - -f 1-3 --complement | rev | ||
| </code> | </code> | ||
| - | Or if you wanted to get the full patch of a file, minus the suffix. | + | Or if you wanted to get the full path of a file, minus the suffix. |
| <code bash> | <code bash> | ||
| echo /proc/config.gz | rev | cut -d. -f1 --complement | rev | echo /proc/config.gz | rev | cut -d. -f1 --complement | rev | ||
| Line 97: | Line 97: | ||
| bash-4.2$ | bash-4.2$ | ||
| </code> | </code> | ||
| - | Clearly you need to quote a file with spaces. You could use single quotes here, because no variable were inside the quotes. You should not quote in this case: | + | Clearly you need to quote a file with spaces. You could use single quotes here, because no variables were inside the quotes. You should not quote in this case: |
| <code bash> | <code bash> | ||
| bash-4.2$ for i in $(seq 1 10); do printf "$i "; done; echo; | bash-4.2$ for i in $(seq 1 10); do printf "$i "; done; echo; | ||
| Line 148: | Line 148: | ||
| === External Links === | === External Links === | ||
| * http://www.grymoire.com/Unix/Quote.html | * http://www.grymoire.com/Unix/Quote.html | ||
| - | ==== Regex ==== | + | ==== Regular expressions ==== |
| === Basic === | === Basic === | ||
| * ''.'' matches any single character. | * ''.'' matches any single character. | ||
| Line 174: | Line 174: | ||
| * Example: ''\<[tT]he\>'' matches the word ''the'' or ''The''. | * Example: ''\<[tT]he\>'' matches the word ''the'' or ''The''. | ||
| * ''*'' matches any number of the previous character or nothing = no character. Example: ''[0-9]*'' which will match any number of numbers. ''.*'' matches any number of anything. | * ''*'' matches any number of the previous character or nothing = no character. Example: ''[0-9]*'' which will match any number of numbers. ''.*'' matches any number of anything. | ||
| - | === Extended === | + | === Extended regular expressions === |
| The following must be supported by the program for them to work. For example for grep you must run ''egrep'' or ''grep -E''. | The following must be supported by the program for them to work. For example for grep you must run ''egrep'' or ''grep -E''. | ||
| * ''+'' matches any number of the previous character, like ''*'', but there must be at least one to match, so it will not match nothing or no character. | * ''+'' matches any number of the previous character, like ''*'', but there must be at least one to match, so it will not match nothing or no character. | ||
| Line 184: | Line 184: | ||
| * ''{1,}'' = ''+'' | * ''{1,}'' = ''+'' | ||
| * ''{,1}'' = ''?'' | * ''{,1}'' = ''?'' | ||
| + | === External Links === | ||
| + | * http://www.grymoire.com/Unix/Regular.html | ||
| + | * http://www.regular-expressions.info/ | ||
| + | ==== Useful commands and info ==== | ||
| + | === stat === | ||
| + | Stat is the most accurate way to determine: | ||
| + | * File size in bytes: <code bash>stat -c '%s' file.txt</code> | ||
| + | * File permissions in octal: <code bash>stat -c '%a' file.txt</code> | ||
| + | === awk variable defaults === | ||
| + | An important point is that awk variables are set to zero by default. This may cause problems in some situtations. Example: | ||
| + | <code bash> | ||
| + | echo -ne '-321\n-14\n-1\n-34\n-4\n' | awk 'BEGIN{max=""}{if ($1 > max) max=$1; if ($1 < min) min=$1;}END{print min"\t"max}' | ||
| + | </code> | ||
| + | This works properly because max is set to an empty string and thus has a lower value than any number. Try removing the BEGIN clause and see what happens. Also note that adding ''min=""'' to the BEGIN clause fails as well. | ||
| + | === no data directory test === | ||
| + | You can use this to test if a directory contains no data. For example, it will say ''0'' if the directory only contains empty files and directories = no data. | ||
| + | <code bash> | ||
| + | du -s directory | ||
| + | </code> | ||
| + | === cmp === | ||
| + | This can compare two files byte by byte, and can be more useful than checksums. For example, after you burn a CD/DVD, you can run: | ||
| + | <code bash> | ||
| + | cmp slackware.iso /dev/sr0 | ||
| + | </code> | ||
| + | It should say the following if the disk burned correctly: | ||
| + | <code bash> | ||
| + | cmp: EOF on slackware.iso | ||
| + | </code> | ||
| + | === shell math === | ||
| + | Remember that shell utilities like ''let'' and ''expr'' only do integer math. For floating point use either ''bc'' or ''awk''. | ||
| + | === shell GUI === | ||
| + | There are numerous programs that allow you to create GUIs from a shell script. | ||
| + | * [[http://xdialog.free.fr/|Xdialog is fully dialog compatible.]] | ||
| + | * [[https://sites.google.com/site/easybashgui/home|A function library that increases shell GUI portability.]] | ||
| + | * [[http://code.google.com/p/gtkdialog/|Gtkdialog has advanced features for customized GUIs.]] | ||
| + | === External Links === | ||
| + | * [[http://www.grymoire.com/Unix/|Guide to awk, bash, sed, find, and more]] | ||
| + | * [[http://www.tldp.org/LDP/abs/html/index.html|Advanced bash guide]] | ||
| + | * [[http://www.catonmat.net/projects/cheat-sheets/|Cheat sheets on Linux CLI programs, the main site is also useful]] | ||
| + | * [[http://www.zzee.com/solutions/linux-permissions.shtml|Guide to file permissions]] | ||
| ====== Sources ====== | ====== Sources ====== | ||
| <!-- If you are copying information from another source, then specify that source --> | <!-- If you are copying information from another source, then specify that source --> | ||
| Line 192: | Line 232: | ||
| * I quoted ''man comm'' | * I quoted ''man comm'' | ||
| * I used ''man grep'' for the regex section. | * I used ''man grep'' for the regex section. | ||
| + | * Written by [[wiki:user:htexmexh|H_TeXMeX_H]] | ||
| <!-- Please do not modify anything below, except adding new tags.--> | <!-- Please do not modify anything below, except adding new tags.--> | ||
| <!-- You must remove the tag-word "template" below before saving your new page --> | <!-- You must remove the tag-word "template" below before saving your new page --> | ||
| - | {{tag>howtos software author_htexmexh work_in_progress}} | + | {{tag>howtos software author_htexmexh}} |
