CIS 218 stream editor (sed) CIS 218 Advanced UNIX 1 sed Uses - - PowerPoint PPT Presentation

CIS 218 Advanced UNIX 1

CIS 218 stream editor (sed)

CIS 218 Advanced UNIX 2

sed

• Uses same syntax as vi
• Batch front end to same ed command
• Works record by record thru entire file
• sed [-n] script [filelist]
• r
• sed [-n] -f scriptfile [filelist]
• if no filelist is given, it is often used in a pipe
• script = one or more lines in the following format:

[address[,address]] instruction [argument list]

CIS 218 Advanced UNIX 3

sed

• Addressing can be the same as we saw in vi, but it can also be regular expressions

to match instructions can be any one from the list:

• d - delete
• n - next
• a - append
• i - insert
• c - change
• s - substitute
• p - print
• w - write
• r - read
• q – quit
• to modify the instructions you can also use

– ! - not - to mean if it does not match – { } - to group the instructions together on a single match

• the -n says don't print a line to the output unless specifically instructed to. Default

is to print all lines.

• s (substitute) is the same command specified in vi and regular expressions: s/old/new/[g]

CIS 218 Advanced UNIX 4

sed Examples

• % sed '3,6 p' file - print all lines, duplicates lines 3, 4, 5,

and 6 in the output

• % sed -n '3,6 p' file - will print only the lines 3 thru 6

to the output

• % sed -n '/line/ p' file - will print any lines that contain

the string "line“

• sed commands often put into a sed-script file:

cat pscript 3,6 p

• sed -n -f pscript file will print the lines 3thru 6 to output
• r used in a pipe: who | sed -n -f pscript | more

CIS 218 Advanced UNIX 5

Sed remembering what was found

• Things enclosed in the \( \) pair will be stored (up to 9) to be used as \1 , \2 ...

\9

• % cat rev.script

s/^\([0-9]\)\([0-9]\)/\2and\1/

• % cat num.file

23 Jan 43 Pete 72 Fred 91 Mike

• % sed -f rev.script numfile

32 Jan 34 Pete 27 Fred 19 Mike