Common shell commands
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Text file manipulation
Extract each 10th line from a file with 5000 lines
$ perl -we 'while(<STDIN>){$.==$ARGV[0]&&print&&shift&&(@ARGV||exit)}' `seq 1 10 5000`
Squeeze white spaces
$ sed -r -e "s/ +/ /g" inputFile
or even simpler
$ tr -s ' ' < inputFile
Sum numbers
$ cat numbers
23
1
145
33
999
$ cat numbers | awk '{s+=$1} END {print s}'
1201
Delete lines by pattern
Delete all lines which end with /CVS from a file
$ sed -e '\,.*/CVS,d' inputfile
Delete all empty lines
sed -e '/^$/d' inputfile
Disable the audio bell
setterm -bfreq 0
Switch columns in a text file
$ cat my.txt X1 X2 A1 A2 Z1 Z2
Desired output:
$ cat my.txt X2 X1 A2 A1 Z2 Z1
Solution:
$ cat my.txt | awk '{print $2, $1}'
X2 X1
A2 A1
Z2 Z1
Additional sed tips: http://www.tty1.net/sed-tutorium/html/ar01s03.html
find
Find all c and cpp files and search a word in them
$ find . \( -name "*.c" -o -name "*.cpp" \) -exec grep "main" {} \; -print
grep
sed
The basic sed algorithm
awk
The basic awk algorithm
cpio
- List contents of cpio archive
$ cpio -tv < file.cpio
- Extract cpio archive
$ cpio -idmv < file.cpio
Redirection
sh like shells
Redirect both standard input and standard error to file:
$ ls > dirlist 2>&1
Pipe both standard output and standard error to standard input of other application:
$ ls 2>& 1 | more
In any case, you can be sure that you always end up with files which are called "1" or "2" whenever you try these things...
csh like shells
Do not use them (http://www.littletux.net/serendipity/index.php?/archives/13-The-csh-madness.html). If you are forced to:
Pipe both standard output and standard error to standard input of other application:
% runSomeApp |& more
Sub shells and variables
rsync
rsync 2.6.2
$ rsync -a --files-from=/tmp/foo /usr remote:/backup
If /tmp/foo contains the string "bin" (or even "/bin"), the /usr/bin directory will be created as /backup/bin on the remote host (but the contents of the /usr/bin dir would not be sent unless you specified -r or the names were explicitly listed in /tmp/foo)
rsync 2.6.6
$ rsync -a --files-from=/tmp/foo /usr remote:/backup
If /tmp/foo contains the string "bin" (or even "/bin"), the /usr/bin directory will be created as /backup/bin on the remote host. If it contains "bin/" (note the trailing slash), the immediate contents of the directory would also be sent (without needing to be explicitly mentioned in the file -- this began in version 2.6.4)
Inclusion and exclusion patterns
The list of inclusion and exclusion patterns is processed one pattern after the other. As soon as a pattern matches, the list iteration stops and the action (include or exclude) associated to the pattern is performed.
