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May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
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Commands tagged redirection from sorted by
Terminal - Commands tagged redirection - 17 results
command foo bar | sudo tee /etc/write-protected > /dev/null
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); }

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.

function brainwallet_checksum () { (o='openssl sha256 -binary'; p='printf';($p %b "\x80";$p %s "$1"|$o)|$o|sha256sum|cut -b1-8); }

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

function brainwallet_exponent () { printf %s "$1"|sha256sum|head -c 64; }
2014-02-18 01:49:09
User: nixnax
Functions: head printf

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

quietly() { "$@" > /dev/null 2>&1; }
exec 2>&1
2010-08-05 08:24:18
User: redy
Functions: exec

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...


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. :)

tee >(cat - >&2)
2010-07-20 17:22:31
User: camocrazed
Functions: cat tee

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

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
2010-04-02 09:43:32
User: mtron
Functions: grep read sed wc wget

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.

wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;"
2010-03-30 23:49:30
User: tali713
Functions: grep sed wget

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.

2010-02-06 18:35:10
User: drewk

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.

echo "vertical text" | fold -1
echo "vertical text" | grep -o '.'
2009-09-11 03:45:04
User: dennisw
Functions: echo grep

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")
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 }
2009-07-27 20:21:15
User: Josay
Functions: cat echo mv rm tty
Tags: redirection

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...

lynx -dump randomfunfacts.com | grep -A 3 U | sed 1D
2009-05-05 07:52:10
User: xizdaqrian
Functions: grep sed

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.

gnuplot -persist <(echo "plot '<(sort -n listOfNumbers.txt)' with lines")
2009-05-02 13:46:02
User: penthief
Functions: echo

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.

command > tmp && cat logfile.txt >> tmp && tmp > logfile.txt && rm tmp
2009-04-05 22:00:32
User: akoumjian
Functions: cat command rm

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.

awk '{print > $3".txt"}' FILENAME
2009-03-31 15:14:13
User: alperyilmaz
Functions: awk

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:


foo foo A foo

lorem ipsum A lorem

and B.txt will be

bar bar B bar