Commands using cat (514)
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extract data in multiline blocks of data with perl pattern matching loop Show Sample Output
1cat z.log | perl -ne 'BEGIN{ print "DATE;RATE\n"; } /\[(\d.*)\]/ && print $1; /CURRENT RATE: +(\S+) msg.*/ && print ";" .$1 . "\n"; ' -
1cat urls.txt | wget -i- -T 10 -t 3 --waitretry 1
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Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it. Show Sample Output
1cat /dev/urandom|od -t x1|awk 'NR > line { pos=int(rand()*15)+2;printf("%s",$pos);line=NR+(rand()*1000);digits = digits+2 } digits == 64 { print("\n");exit }' -
Generate a 18 character password from character set a-zA-Z0-9 from /dev/urandom, pipe the output to Python which prints the password on standard out and in crypt sha512 form. Show Sample Output
1cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 18 | head -1 | python -c "import sys,crypt; stdin=sys.stdin.readline().rstrip('\n'); print stdin;print crypt.crypt(stdin)" -
1cat somefile | tee >(openssl md5 > sum.md5) | bzip2 > somefile.bz2
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1find . -type f -name "*.txt" | while read; do (($(cat $THISFILE | wc -l) < 10)) && rm -vf "$THISFILE"; done
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CPU flags: rm --> 16-bit processor (real mode) tm --> 32-bit processor (? mode) lm --> 64-bit processor (long mode)
1cat /proc/cpuinfo | grep " lm " > /dev/null && echo 64 bits || echo 32 bits -
1OIFS=$IFS;IFS=$':';for i in $(cat -n /etc/passwd);do echo -n $i\ ** \ ;done
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For situations where you keep JSON in a VCS and you want your diffs to be sane, such as within a Chef configuration repo.
1cat foo.json | python -mjson.tool -
Count your source and header file's line numbers. This ignores blank lines, C++ style comments, single line C style comments. This will not ignore blank lines with tabs or multiline C style comments.
1find /usr/include/ -name '*.[c|h]pp' -o -name '*.[ch]' -print0 | xargs -0 cat | grep -v "^ *$" | grep -v "^ *//" | grep -v "^ */\*.*\*/" | wc -l -
Show's per IP of how many requests they did to the Apache webserver
1cat /var/log/apache2/access_logs | cut -d ' ' -f 1 | uniq -c | sort -n -
The first sort is necessary for ips in a list to be actually unique.
1cat /var/log/apache2/access_logs | cut -d' ' -f1 | sort | uniq -c | sort -n -
Prepend text to a file. It doen't need temporary files, ed or sed.
1echo "text to prepend" | cat - file -
1find . -name "*.URL" | while read file ; do cat "$file" | sed 's/InternetShortcut/Desktop Entry/' | sed '/^\(URL\|\[\)/!d' > "$file".desktop && echo "Type=Link" >> "$file".desktop ; done
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1( find ./ -name '*.rb' -print0 | xargs -0 cat ) | wc -l
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on some distro's you have to replace "BogoMIPS" with "bogomips". Show Sample Output
1cat /proc/cpuinfo | grep BogoMIPS | uniq | sed 's/^.*://g' | awk '{print($1 / 4) }' -
1cat skype_log | sed -s 's/\(\[.*\]\) \(.*\): \(.*\)/<\2> \3/'
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The command will read the apache log file and fetch the virtual host requested and the number of requests.
1cat /etc/httpd/logs/access.log | awk '{ print $6}' | sed -e 's/\[//' | awk -F'/' '{print $1}' | sort | uniq -c -
Lots of scripts show you how to use socat to send an email to an SMTP server; this command actually emulates an SMTP server! It assumes the client is only sending to one recipient, and it's not at all smart, but it'll capture the email into a log file and the client will stop retrying. I used this to diagnose what emails were being sent by cron and subsequently discarded, but you can use it for all sorts of things. Show Sample Output
1socat TCP4-LISTEN:25,fork EXEC:'bash -c \"echo 220;sleep 1;echo 250;sleep 1;echo 250;sleep 1;echo 250;sleep 1;echo 354;sleep 1;echo 250; timeout 5 cat >> /tmp/socat.log\"' -
This checks the system load every second and if it's over a certain threshold (.8 in this example), it spits out the date, system loads and top 4 processes sorted by CPU. Additionally, the \a in the first echo creates an audible bell.
1while sleep 1; do if [ $(echo "$(cat /proc/loadavg | cut -d' ' -f1) > .8 " | bc) -gt 0 ]; then echo -e "\n\a"$(date)" \e[5m"$(cat /proc/loadavg)"\e[0m"; ps aux --sort=-%cpu|head -n 5; fi; done -
1a=$(b=$(($LINES/2));f() { for c in $(seq $b); do for i in $(seq $c);do echo x;done|xargs echo;done };paste <(f) <(f|tac|tr 'x' '-') <(f|tac|tr 'x' '-') <(f)|tr '\t' ' ');(cat <<<"$a"|tac;cat <<<"$a")|tr '-' ' '
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It's useful when you cannot access your env (systemd) or the process DISPLAY variable is not set. Perhaps also when you have a multi-head/user configuration. Show Sample Output
1for p in $(pgrep -t $(cat /sys/class/tty/tty0/active)); do d=$(awk -v RS='\0' -F= '$1=="DISPLAY" {print $2}' /proc/$p/environ 2>/dev/null); [[ -n $d ]] && break; done; echo $d -
retrieve file names back from touch commands for them Show Sample Output
1touch files.txt; cat reorder_files.sh | while read line; do x=`echo $line | sed 's/touch \([a-z0-9\.]\+.*.pdf\);.*/\1/'`; echo $x >> files.txt ; done; -
Create a bash script to change the modification time for each file in 'files.txt' such that they are in the same order as in 'files.txt' File name for bash script specified by variable, 'scriptName'. It is made an executable once writing into it has been completed. Show Sample Output
1scriptName="reorder_files.sh"; echo -e '#!/bin/sh\n' > "${scriptName}"; cat files.txt | while read file; do echo "touch ${file}; sleep 0.5;" >> "${scriptName}"; done; chmod +x "${scriptName}"; -
1cat matching_files.txt | xargs sed -i '' "s/require('global-module')/require('..\/some-folder\/relative-module')/"
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