os_cp:redirects_pipes
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os_cp:redirects_pipes [2025/03/26 15:44] jkonczak |
os_cp:redirects_pipes [2026/03/24 14:33] (current) jkonczak [more, less] |
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| ==== Printing text ==== | ==== Printing text ==== | ||
| - | ''**echo** //text//'' outputs //text// followed by a newline (unless ''-n'' is specified). \\ | + | ''**echo** //text//'' outputs //text// followed by a newline. \\ |
| - | The ''-e'' switch turns backslash escapes into corresponding characters, e.g., ''\t'' | + | <small> |
| - | becomes a tab and ''\n'' a newline (cf. manual). | + | ''echo'' is present in almost any shell of any operating system, |
| + | but there is no consensus on how to interpret switches and how to treat | ||
| + | backslashes in the text. | ||
| + | \\ | ||
| + | In Bash, the ''-n'' switch supresses the newline, and ''-e'' turns backslash | ||
| + | escapes into corresponding characters, e.g., ''\t'' becomes a tab and ''\n'' | ||
| + | a newline (cf. manual). | ||
| + | </small> | ||
| ''**printf** //format// [//arguments//]...'' works roughly the same as the ''printf'' function in C. | ''**printf** //format// [//arguments//]...'' works roughly the same as the ''printf'' function in C. | ||
| <small> | <small> | ||
| - | ''**figlet** [//text//]'' outputs //text// or the standard input by using ascii-art font. | + | Here and there, the course materials make use of the following toy commands: |
| + | \\ | ||
| + | ''**figlet** [//text//]'' outputs //text// or the standard input by using an ascii-art font. | ||
| + | \\ | ||
| ''**cowsay** [//text//]'' makes a cow say the //text// (or the standard input). | ''**cowsay** [//text//]'' makes a cow say the //text// (or the standard input). | ||
| </small> | </small> | ||
| Line 60: | Line 69: | ||
| ++++ Examples | {{page>so:redirects:echo&inline}} ++++ | ++++ Examples | {{page>so:redirects:echo&inline}} ++++ | ||
| - | ~~Exercise.#~~ Try ''echo -e 'foo\n\nbaz' '' \\ and ''echo -e '\n\n one \033[A \033[A two \033[B \033[B \n \033[1;31m red \033[0m' '' \\ <small>[[https://en.wikipedia.org/wiki/ANSI_escape_code|ANSI escape codes]] are well summarized [[https://gist.github.com/fnky/458719343aabd01cfb17a3a4f7296797|here]]</small> | + | ~~Exercise.#~~ Try the commands ''echo -e 'foo\n\nbaz' '' \\ and ''echo -e '\n\n one \033[A \033[A two \033[B \033[B \n \033[1;31m red \033[0m' '' \\ <small>[[https://en.wikipedia.org/wiki/ANSI_escape_code|ANSI escape codes]] are well summarized [[https://gist.github.com/fnky/458719343aabd01cfb17a3a4f7296797|here]]</small> |
| ~~Exercise.#~~ Try ''printf "|%4.2f|%3s|%-20s|\n|%4.2f|%3s|%-20s|\n" 3.1428 pi circumference/radius 9.8 g gravity'' | ~~Exercise.#~~ Try ''printf "|%4.2f|%3s|%-20s|\n|%4.2f|%3s|%-20s|\n" 3.1428 pi circumference/radius 9.8 g gravity'' | ||
| Line 173: | Line 182: | ||
| ~~Exercise.#~~ Redirect standard output and the standard error of the ''find /var/spool/'' command to the same file. | ~~Exercise.#~~ Redirect standard output and the standard error of the ''find /var/spool/'' command to the same file. | ||
| + | |||
| + | ++++ Examples | {{page>so:redirects:out-en&inline}} ++++ | ||
| === Input redirections === | === Input redirections === | ||
| Line 201: | Line 212: | ||
| ~~Exercise.#~~ Use ''bc'' to calculate ''sqrt(2.0000)'' in non-interactive mode and redirect its output to a file. | ~~Exercise.#~~ Use ''bc'' to calculate ''sqrt(2.0000)'' in non-interactive mode and redirect its output to a file. | ||
| + | |||
| + | ++++ Examples | {{page>so:redirects:in&inline}} ++++ | ||
| <small> | <small> | ||
| Line 335: | Line 348: | ||
| \\ Then repeat the commands, running the ''ps'' before the ''fold''. | \\ Then repeat the commands, running the ''ps'' before the ''fold''. | ||
| </small> | </small> | ||
| + | |||
| + | ++++ Examples | {{page>so:redirects:pipes1-en&inline}} ++++ | ||
| ===== Filters ===== | ===== Filters ===== | ||
| Line 363: | Line 378: | ||
| ~~Exercise.#~~ Run ''seq 25 > //file//''. Then run ''tail -f //file//'' in one | ~~Exercise.#~~ Run ''seq 25 > //file//''. Then run ''tail -f //file//'' in one | ||
| terminal and append (with output redirection) some data to //file//. | terminal and append (with output redirection) some data to //file//. | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:head_tail&inline}} ++++ | ||
| ==== grep ==== | ==== grep ==== | ||
| Line 374: | Line 391: | ||
| <small> | <small> | ||
| The ''grep'' program accepts several regular expression grammars. | The ''grep'' program accepts several regular expression grammars. | ||
| - | POSIX [[https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html|specifies]] | + | POSIX [[https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap09.html|specifies]] |
| basic (default for ''grep'') and extended regular expressions (selectable with | basic (default for ''grep'') and extended regular expressions (selectable with | ||
| ''egrep'' or ''grep -E'' ). See manual for your implementation of ''grep'' for | ''egrep'' or ''grep -E'' ). See manual for your implementation of ''grep'' for | ||
| Line 409: | Line 426: | ||
| \\ | \\ | ||
| List all files containing ''ecdsa'' in ''~/.ssh''. | List all files containing ''ecdsa'' in ''~/.ssh''. | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:grep&inline}} ++++ | ||
| ==== cut ==== | ==== cut ==== | ||
| Line 430: | Line 449: | ||
| ''egrep '^[Ee]{2}' /usr/share/myspell/en_US.dic'' a slash and all that follows | ''egrep '^[Ee]{2}' /usr/share/myspell/en_US.dic'' a slash and all that follows | ||
| it. | it. | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:cut-en&inline}} ++++ | ||
| ==== sort ==== | ==== sort ==== | ||
| Line 474: | Line 495: | ||
| ~~Exercise.#~~ Sort the file by the second column (alphabetically) and by the third column (numerically). | ~~Exercise.#~~ Sort the file by the second column (alphabetically) and by the third column (numerically). | ||
| </small> | </small> | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:sort&inline}} ++++ | ||
| ==== wc, uniq, nl ==== | ==== wc, uniq, nl ==== | ||
| Line 506: | Line 529: | ||
| \\ | \\ | ||
| Then pipe it through ''sort'' and ''uniq'' so that you see how many times each result was hit. | Then pipe it through ''sort'' and ''uniq'' so that you see how many times each result was hit. | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:wc_uniq&inline}} ++++ | ||
| <small> | <small> | ||
| Line 540: | Line 565: | ||
| * to squeeze all spaces | * to squeeze all spaces | ||
| * remove all the letters ''rwx'' | * remove all the letters ''rwx'' | ||
| + | |||
| + | ++++ Examples | {{page>so:pipes_filters:tr-en&inline}} ++++ | ||
| <small> | <small> | ||
| Line 582: | Line 609: | ||
| not human-readable file format. | not human-readable file format. | ||
| \\ | \\ | ||
| - | ''[[https://github.com/wofr06/lesspipe|lesspipe]]'' is the leading implementation | + | ''[[https://lesspipe.org|lesspipe]]'' is the leading implementation |
| of this feature. | of this feature. | ||
| </small> | </small> | ||
os_cp/redirects_pipes.1743000284.txt.gz · Last modified: 2025/03/26 15:44 by jkonczak
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