Commands tagged redirection (17)

  • Useful when you've produced a large file of numbers, and want to quickly see the distribution. The value of y halfway along the x axis is the median. Simple! Just create the listOfNumbers.txt file with a number on each line to try it out.


    22
    gnuplot -persist <(echo "plot '<(sort -n listOfNumbers.txt)' with lines")
    penthief · 2009-05-02 13:46:02 3
  • Though without infinite time and knowledge of how the site will be designed in the future this may stop working, it still will serve as a simple straight forward starting point. This uses the observation that the only item marked as strong on the page is the single logical line that includes the italicized fact. If future revisions of the page show failure, or intermittent failure, one may simply alter the above to read. wget randomfunfacts.com -O - 2>/dev/null | tee lastfact | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;" The file lastfact, can then be examined whenever the command fails.


    13
    wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;"
    tali713 · 2010-03-30 23:49:30 1
  • Define a function vert () { echo $1 | grep -o '.'; } Use it to print some column headers paste <(vert several) <(vert parallel) <(vert vertical) <(vert "lines of") <(vert "text can") <(vert "be used") <(vert "for labels") <(vert "for columns") <(vert "of numbers") Show Sample Output


    12
    echo "vertical text" | grep -o '.'
    dennisw · 2009-09-11 03:45:04 1
  • You have a script where =ALL= STDERR should be redirected to STDIN and you don't want to add "2>&1" at the end of each command... E.G.: ls -al /foo/bar 2>&1 Than just add this piece of code at the beginning of your script! I hope this can help someone. :)


    9
    exec 2>&1
    redy · 2010-08-05 08:24:18 0
  • Bash has a great history system of its commands accessed by the ! built-in history expansion operator (documented elsewhere on this site or on the web). You can combine the ! operator inside the process redirection Very handy. Show Sample Output


    7
    <(!!)
    drewk · 2010-02-06 18:35:10 2
  • A bitcoin "brainwallet" is a secret passphrase you carry in your brain. The Bitcoin Brainwallet Private Key Base58 Encoder is the third of three functions needed to calculate a bitcoin PRIVATE key from your "brainwallet" passphrase. This base58 encoder uses the obase parameter of the amazing bc utility to convert from ASCII-hex to base58. Tech note: bc inserts line continuation backslashes, but the "read s" command automatically strips them out. I hope that one day base58 will, like base64, be added to the amazing openssl utility. Show Sample Output


    6
    function b58encode () { local b58_lookup_table=({1..9} {A..H} {J..N} {P..Z} {a..k} {m..z}); bc<<<"obase=58;ibase=16;${1^^}"|(read -a s; for b58_index in "${s[@]}" ; do printf %s ${b58_lookup_table[ 10#"$b58_index" ]}; done); }
    nixnax · 2014-02-18 02:29:30 0
  • the tee command does fine with file names, but not so much with file descriptors, such as &2 (stderr). This uses process redirection to tee to the specified descriptor. In the sample output, it's being used to tee to stderr, which is connected with the terminal, and to wc -l, which is also outputting to the terminal. The result is the output of bash --version followed by the linecount Show Sample Output


    5
    tee >(cat - >&2)
    camocrazed · 2010-07-20 17:22:31 3
  • A bitcoin "brainwallet" is a secret passphrase you carry in your brain. The Bitcoin Brainwallet Exponent Calculator is one of three functions needed to calculate the bitcoin PRIVATE key. Roughly, the formula is exponent = sha256 (passphrase) Note that this is a bash function, which means you have to type its name to invoke it. You can check the accuracy of the results here http://brainwallet.org Show Sample Output


    5
    function brainwallet_exponent () { printf %s "$1"|sha256sum|head -c 64; }
    nixnax · 2014-02-18 01:49:09 0
  • A bitcoin "brainwallet" is a secret passphrase you carry in your brain. The Bitcoin Brainwallet Exponent Calculator is the second of three functions needed to calculate a bitcoin PRIVATE key. Roughly, checksum is the first 8 hex digits of sha256(sha256(0x80+sha256(passphrase))) Note that this is a bash function, which means you have to type its name to invoke it Show Sample Output


    5
    function brainwallet_checksum () { (o='openssl sha256 -binary'; p='printf';($p %b "\x80";$p %s "$1"|$o)|$o|sha256sum|cut -b1-8); }
    nixnax · 2014-02-18 02:07:02 0

  • 3
    echo "vertical text" | fold -1
    zude · 2009-10-05 23:20:14 0
  • This works even if there are spaces in any word in the command line. Show Sample Output


    3
    quietly() { "$@" > /dev/null 2>&1; }
    wipu · 2011-10-04 06:45:42 1
  • This command will sort the contents of FILENAME by redirecting the output to individual .txt files in which 3rd column will be used for sorting. If FILENAME contents are as follows: foo foo A foo bar bar B bar lorem ipsum A lorem Then two files called A.txt and B.txt will be created and their contents will be: A.txt foo foo A foo lorem ipsum A lorem and B.txt will be bar bar B bar


    2
    awk '{print > $3".txt"}' FILENAME
    alperyilmaz · 2009-03-31 15:14:13 0
  • A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file. It can be easily avoided because of : 1) warnings "-bash: file.txt: cannot overwrite existing file" 2) options (often "-i") that let the command directly modify the file but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file. Lots of things could probably done in a better way, if you know one... Show Sample Output


    2
    buffer () { tty -s && return; tmp=$(mktemp); cat > "${tmp}"; if [ -n "$1" ] && ( ( [ -f "$1" ] && [ -w "$1" ] ) || ( ! [ -a "$1" ] && [ -w "$(dirname "$1")" ] ) ); then mv -f "${tmp}" "$1"; else echo "Can't write in \"$1\""; rm -f "${tmp}"; fi }
    Josay · 2009-07-27 20:21:15 3
  • extension to tali713's random fact generator. It takes the output & sends it to notify-osd. Display time is proportional to the lengh of the fact.


    2
    wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;" | while read FUNFACT; do notify-send -t $((1000+300*`echo -n $FUNFACT | wc -w`)) -i gtk-dialog-info "RandomFunFact" "$FUNFACT"; done
    mtron · 2010-04-02 09:43:32 1
  • This is a working version, though probably clumsy, of the script submitted by felix001. This works on ubuntu and CygWin. This would be great as a bash function, defined in .bashrc. Additionally it would work as a script put in the path. Show Sample Output


    0
    lynx -dump randomfunfacts.com | grep -A 3 U | sed 1D
    xizdaqrian · 2009-05-05 07:52:10 8
  • Use tee -a to append.


    0
    command foo bar | sudo tee /etc/write-protected > /dev/null
    adeverteuil · 2015-02-08 03:58:35 0
  • Adds the stdout (standard output) to the beginning of logfile.txt. Change "command" to whatever command you like, such as 'ls' or 'date', etc. It does this by adding the output to a temporary file, then adding the previous contents of logfile.txt to the temp file, then copying the new contents back to the logfile.txt and removing the temp file.


    -2
    command > tmp && cat logfile.txt >> tmp && tmp > logfile.txt && rm tmp
    akoumjian · 2009-04-05 22:00:32 7

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