os_cp:redirects_pipes
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os_cp:redirects_pipes [2023/03/23 22:28] jkonczak |
os_cp:redirects_pipes [2026/03/24 01:04] (current) 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). | ||
| Line 25: | Line 28: | ||
| ''**od** [-t x1]'', ''**hexdump** [-C]'', and ''**xxd**'' show binary files. | ''**od** [-t x1]'', ''**hexdump** [-C]'', and ''**xxd**'' show binary files. | ||
| </small> | </small> | ||
| + | |||
| + | ++++ Examples | {{page>so:redirects:cat&inline}} ++++ | ||
| ~~Exercise.#~~ Print any file with ''cat''. Print two files at once with ''cat''. \\ | ~~Exercise.#~~ Print any file with ''cat''. Print two files at once with ''cat''. \\ | ||
| Line 41: | Line 46: | ||
| ==== 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). | + | The ''echo'' command 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> | ||
| - | ~~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> | + | ++++ Examples | {{page>so:redirects:echo&inline}} ++++ |
| + | |||
| + | ~~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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| \\ | \\ | ||
| With the ''-w'' switch, ''seq'' makes all number of equal width (e.g., ''seq -w 8 11'' outputs 08, 09, 10 and 11). | With the ''-w'' switch, ''seq'' makes all number of equal width (e.g., ''seq -w 8 11'' outputs 08, 09, 10 and 11). | ||
| + | |||
| + | ++++ Examples | {{page>so:redirects:seq&inline}} ++++ | ||
| ~~Exercise.#~~ Generate a sequence of numbers from 1 to 15. | ~~Exercise.#~~ Generate a sequence of numbers from 1 to 15. | ||
| Line 164: | 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 192: | 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 214: | Line 236: | ||
| | ''>>'' | opens //word// for appending and replaces //file_number// with the file | | | ''>>'' | opens //word// for appending and replaces //file_number// with the file | | ||
| | ''<>'' | opens //word// for reading and writing and replaces //file_number// with the file | | | ''<>'' | opens //word// for reading and writing and replaces //file_number// with the file | | ||
| - | | ''<<'' | 1) creates a temporary file \\ 2) reads an input line \\ 3) if the line is //word//, go to step 6 \\ 4) if there are no quotes (a pair of ''"'' or <html><code>'</code></html>) in //word//, performs the expansion((E.g., ''$VAR'' is substituted with its value, ''`date`'' is replaced by output of the date command etc.)) on the line \\ 5) writes the line to the temporary file \\ 6) opens the temporary file for reading \\ 7) replace //file_number// with the file \\ The command is run once this is done | | + | | ''<<'' | 1) creates a temporary file \\ 2) reads an input line \\ 3) if the line is //word//, goes to step 7 \\ 4) if there are no quotes (a pair of ''"'' or <html><code>'</code></html>) enclosing the //word//, performs the expansion((E.g., ''$VAR'' is substituted with its value, ''`date`'' is replaced by output of the date command etc.)) on the line \\ 5) appends the line to the temporary file \\ 6) goes to step 2 \\ 7) opens the temporary file for reading \\ 8) replace //file_number// with the file \\ The command is run once this is done | |
| | ''<<-''| same as ''<<'', but after step 2 adds a step: \\ 2a) erase all leading tab characters (''\t'') \\ warning: spaces are not erased | | | ''<<-''| same as ''<<'', but after step 2 adds a step: \\ 2a) erase all leading tab characters (''\t'') \\ warning: spaces are not erased | | ||
| | ''<<<''| warning: this is a Bash extension \\ 1) creates a temporary file \\ 2) writes //word// to it \\ 3) writes a newline to it \\ 4) opens the temporary file for reading \\ 5) replace //file_number// with the file \\ The command is run once this is done | | | ''<<<''| warning: this is a Bash extension \\ 1) creates a temporary file \\ 2) writes //word// to it \\ 3) writes a newline to it \\ 4) opens the temporary file for reading \\ 5) replace //file_number// with the file \\ The command is run once this is done | | ||
| - | | ''<&'' | if //word// is a number: duplicates a readable descriptor number //word// to the number //file_number// \\ if //word/// is ''-'': closes a descriptor number //file_number// | | + | | ''<&'' | if //word// is a number: duplicates a readable descriptor number //word// to the number //file_number// \\ if //word// is ''-'': closes a descriptor number //file_number// | |
| - | | ''>&'' | if //word// is a number: duplicates a writeable descriptor number //word// to the number //file_number// \\ if //word/// is ''-'': closes a descriptor number //file_number// | | + | | ''>&'' | if //word// is a number: duplicates a writeable descriptor number //word// to the number //file_number// \\ if //word// is ''-'': closes a descriptor number //file_number// | |
| | ''&>'' | warning: this is a Bash extension \\ warning: this does not allow providing //file_number// (in fact, ''&'' is the file number) \\ opens //word// for writing, truncates it and replaces streams 1 and 2 with the file | | | ''&>'' | warning: this is a Bash extension \\ warning: this does not allow providing //file_number// (in fact, ''&'' is the file number) \\ opens //word// for writing, truncates it and replaces streams 1 and 2 with the file | | ||
| | ''&>>''| warning: this is a Bash extension \\ warning: this does not allow providing //file_number// (in fact, ''&'' is the file number) \\ opens //word// for appending and replaces streams 1 and 2 with the file | | | ''&>>''| warning: this is a Bash extension \\ warning: this does not allow providing //file_number// (in fact, ''&'' is the file number) \\ opens //word// for appending and replaces streams 1 and 2 with the file | | ||
| Line 234: | Line 256: | ||
| standard output (unless you dare to face the consequences). | standard output (unless you dare to face the consequences). | ||
| - | ~~Exercise.#~~ Swap standard input with standard output of the | + | ~~Exercise.#~~ Swap standard error with standard output of the |
| ''cat /etc/motd /etc/shadow'' command. Test if you did this correctly by adding | ''cat /etc/motd /etc/shadow'' command. Test if you did this correctly by adding | ||
| ''|rev'' at the end (that will put standard output backwards). | ''|rev'' at the end (that will put standard output backwards). | ||
| Line 324: | Line 346: | ||
| ~~Exercise.#~~ Create a named pipe //p//. Redirect input of ''fold'' from //p// | ~~Exercise.#~~ Create a named pipe //p//. Redirect input of ''fold'' from //p// | ||
| in one terminal, and redirect output of ''ps -eF'' to //p// in another terminal. | in one terminal, and redirect output of ''ps -eF'' to //p// in another terminal. | ||
| - | \\ 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 354: | 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 400: | 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 406: | Line 434: | ||
| bytes (''-b //spec//'') / fields (''-f //spec//'') in each line. | bytes (''-b //spec//'') / fields (''-f //spec//'') in each line. | ||
| \\ | \\ | ||
| - | A filed is any number of characters separated by a single-character | + | A field is any number of characters separated by a single-character |
| delimiter (''-d //delim//'', defaults to tab). | delimiter (''-d //delim//'', defaults to tab). | ||
| Line 421: | 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 465: | 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 497: | 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 531: | 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> | ||
os_cp/redirects_pipes.1679606889.txt.gz · Last modified: 2023/03/23 22:28 by jkonczak
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