remove middle lines from file using sed
Posted in Shell Scripting on December 17th, 2013 No Comments »
to remove lines 2 through 18 of file foo.bar, call: sed -e ’2,18d’ foo.bar
Posted in Shell Scripting on December 17th, 2013 No Comments »
to remove lines 2 through 18 of file foo.bar, call: sed -e ’2,18d’ foo.bar
Posted in Shell Scripting on September 12th, 2011 No Comments »
if you find that sed isn’t matching \t, the easiest workaround is to not use sed at all. instead, install ‘gsed’, which can handle tabs.
Posted in Shell Scripting, Unix on August 1st, 2011 No Comments »
i’ve got a bunch of files with one line — a number — and i’d like to sort those filenames on the command line based on that number. to that in one line of shell code: for i in `ls *.*`; do echo “`head -n1 $i` $i” ; done | sort -n
Posted in Shell Scripting on February 14th, 2008 1 Comment »
to send the standard output and standard error streams from your shell script somewhere, place the following at the top of your script: #!/bin/bash exec &> output.file; [the rest of your code]
Posted in Shell Scripting, Unix on October 31st, 2007 No Comments »
to measure how much time a program takes to execute from the command-line, use the ‘time’ function. for instance, to time the ‘date’ command: >> time date Wed Oct 31 14:12:41 EDT 2007 real   0m0.003s user   0m0.000s sys    0m0.002s
Posted in Shell Scripting on October 15th, 2007 2 Comments »
to count the number of times you match a substring in a larger text file, you can use the following shell one-liner: >> sed “s/[sub_str]/[sub_str]\n/g” [text_file] | wc -l
Posted in Shell Scripting on July 11th, 2007 1 Comment »
to spread a one-line command over multiple lines in a shell script, end each line with a slash and indent the next line. for instance: cat $1 | sed ‘s/>FALF/F_FAL/g’ \ | sed ‘s/>FAL1/1_FAL/g’ \ | sed ‘s/>FAL5/5_FAL/g’ \ | sed ‘s/>FALZ/Z_FAL/g’ \ | sed ‘s/>OUTGROUP/5_OUTGROUP/’ > $2
Posted in Shell Scripting on May 1st, 2007 3 Comments »
turns out floating point division (or any other type of floating point math) isn’t built-into the bash shell. instead, you’ll have to use the bc utility: echo “6.0/10″ | bc -l
Posted in Shell Scripting on February 12th, 2007 1 Comment »
file existence can be tested for in a conditional using the -a operator: if [ -a filename.txt ] then echo “file here!” fi
Posted in Shell Scripting on February 12th, 2007 34 Comments »
let’s say you’ve got: $j=”foo” and you’d like to tack on its good partner ‘bar’. then, use the dollar sign and curly braces to delineate variable from string: $k=”${j}bar”