Jan Kończak

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os_cp:redirects_pipes [2024/03/19 22:33] – [Pipes] jkonczakos_cp:redirects_pipes [2026/03/24 13:33] (current) – [more, less] jkonczak
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 <small> <small>
 +''**join** [-t //separator//] [-1 //fieldNumberInFile1//] [-2 //fieldNumberInFile2//] //file1// //file2//''
 +parses two sorted files and prints their lines joined on specified fields. 
 +
 ''**fold** [-w //width//] [//file//]...'' outputs input files (or standard input) ''**fold** [-w //width//] [//file//]...'' outputs input files (or standard input)
 forcing a line break whenever a line would exceed //width// (that defaults to 80). forcing a line break whenever a line would exceed //width// (that defaults to 80).
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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>
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 ++++ 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''
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 ~~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 ===
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 ~~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>
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 \\ 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 =====
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 ~~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 ====
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 <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
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 \\ \\
 List all files containing ''ecdsa'' in ''~/.ssh''. List all files containing ''ecdsa'' in ''~/.ssh''.
 +
 +++++ Examples | {{page>so:pipes_filters:grep&inline}} ++++
  
 ==== cut ==== ==== cut ====
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 ''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 ====
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 ~~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 ====
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 \\ \\
 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>
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   * 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>
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 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>
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