sed command¶
sed: Stream Editor
Working principle: The sed command will read the currently processed row and place it in the "pattern space" for processing. After processing, the result will be output and the "pattern space" will be cleared. Next, read the next line and place it in the "pattern space" for processing, and so on, until the last line. Some documents also mention a term called "hold space" (also known as "temporary-storage space"), which can temporarily store some processed data and output it through "pattern space".
"pattern space" and "hold space": An area of memory where data is processed and stored.
For information not covered, review the sed manual.
The usage of the command is:
sed [OPTION]... {script-only-if-no-other-script} [input-file]...
| options | description |
|---|---|
| -n | Output text lines that will only be processed by the sed command to the screen |
| -e | Apply multiple sed operation commands to the input text line data |
| -f | Call and execute sed script command file |
| -i | Modify the original file |
| -r | Regular expression |
| Operation command (sometimes called operation instruction) |
description |
|---|---|
| s/regexp/replacement/ | Replacement string |
| p | Print the current "pattern space". Often used with the -n option, for example: cat -n /etc/services \| sed -n '3,5p' |
| d | Delete "pattern space". Start next cycle |
| D | Delete the first line of the "pattern space" and start next cycle |
| = | Print Line Number |
| a \text | Add one or more lines of content after the matching line. When adding multiple lines, all lines except the last line need to use "\" to indicate that the content has not ended |
| i \text | Add one or more lines of content before the matching line. When adding multiple lines, all lines except the last line need to use "\" to indicate that the content is not ended |
| c \text | Replace matching lines with new text |
| q | Immediately exit the sed script |
| r | Append text read from file |
| : label | Label for b and t commands |
| b label | Branch to label; if label is omitted, branch to end of script |
| t label | If "s///" is a successful replacement, then jump to the label |
| h H | Copy/append "pattern space" to "hold space" |
| g G | Copy/append "hold space" to "pattern space" |
| x | Exchange the contents of the hold and pattern spaces |
| l | List out the current line in a "visually unambiguous" form |
| n N | Read/append the next line of input into the "pattern space" |
| w FILENAME | Write the current pattern space to FILENAME |
| ! | negation |
| & | Referencing a string that already matches |
| Addresses | description |
|---|---|
| first~step | Use "first" to specify the first line, and 'step' to specify the step size. For example, outputting odd lines of text with sed -n "1~2p" /etc/services |
| $ | Match the last line of text |
| /regexp/ | Using regular expressions to match text lines |
| number | Specify line number |
| addr1,addr2 | Use line number positioning to match all lines from "addr1" to "addr2" |
| addr1,+N | Use line number positioning to match addr1 and the N lines following addr1 |
Examples of usage¶
-
Match and print (
p)- Print a line that begins with a netbios string
Shell > cat /etc/services | sed -n '/^netbios/p' netbios-ns 137/tcp # NETBIOS Name Service netbios-ns 137/udp netbios-dgm 138/tcp # NETBIOS Datagram Service netbios-dgm 138/udp netbios-ssn 139/tcp # NETBIOS session service netbios-ssn 139/udpTip
As we all know, double and single quotation marks in a shell play different roles. The $, `, and \ in double quotes have a special meaning. The recommendation is to use single quotes more often when using the
sedcommand.- Print the text from lines 23 to 26
Shell > cat -n /etc/services | sed -n '23,26p' 23 tcpmux 1/tcp # TCP port service multiplexer 24 tcpmux 1/udp # TCP port service multiplexer 25 rje 5/tcp # Remote Job Entry 26 rje 5/udp # Remote Job Entry- Print odd lines
Shell > cat -n /etc/services | sed -n '1~2p' 1 # /etc/services: 3 # 5 # IANA services version: last updated 2016-07-08 7 # Note that it is presently the policy of IANA to assign a single well-known 9 # even if the protocol doesn't support UDP operations. 11 # are included, only the more common ones. 13 # The latest IANA port assignments can be gotten from 15 # The Well Known Ports are those from 0 through 1023. 17 # The Dynamic and/or Private Ports are those from 49152 through 65535 19 # Each line describes one service, and is of the form: ...- Print line 10 to the last line
Shell > cat -n /etc/services | sed -n '10,$p' 10 # Updated from RFC 1700, ``Assigned Numbers'' (October 1994). Not all ports 11 # are included, only the more common ones. 12 # 13 # The latest IANA port assignments can be gotten from 14 # http://www.iana.org/assignments/port-numbers 15 # The Well Known Ports are those from 0 through 1023. 16 # The Registered Ports are those from 1024 through 49151 17 # The Dynamic and/or Private Ports are those from 49152 through 65535 ...- Lines 10 to the last do not print
Shell > cat -n /etc/services | sed -n '10,$!p' 1 # /etc/services: 2 # $Id: services,v 1.49 2017/08/18 12:43:23 ovasik Exp $ 3 # 4 # Network services, Internet style 5 # IANA services version: last updated 2016-07-08 6 # 7 # Note that it is presently the policy of IANA to assign a single well-known 8 # port number for both TCP and UDP; hence, most entries here have two entries 9 # even if the protocol doesn't support UDP operations.- Print the line number and content of the matched string
Shell > sed -n -e '/netbios/=' -e '/netbios/p' /etc/services 123 netbios-ns 137/tcp # NETBIOS Name Service 124 netbios-ns 137/udp 125 netbios-dgm 138/tcp # NETBIOS Datagram Service 126 netbios-dgm 138/udp 127 netbios-ssn 139/tcp # NETBIOS session service 128 netbios-ssn 139/udp- Match string range and print it
Use commas to separate string ranges
Shell > cat /etc/services | sed -n '/^netbios/,/^imap/p' netbios-ns 137/tcp # NETBIOS Name Service netbios-ns 137/udp netbios-dgm 138/tcp # NETBIOS Datagram Service netbios-dgm 138/udp netbios-ssn 139/tcp # NETBIOS session service netbios-ssn 139/udp imap 143/tcp imap2 # Interim Mail Access Proto v2Info
Start of range: Match the line where the string is located, only matching the first string that appears. End of range: Match the line where the string is located, only matching the first string that appears.
Shell > grep -n ^netbios /etc/services 123:netbios-ns 137/tcp # NETBIOS Name Service 124:netbios-ns 137/udp 125:netbios-dgm 138/tcp # NETBIOS Datagram Service 126:netbios-dgm 138/udp 127:netbios-ssn 139/tcp # NETBIOS session service 128:netbios-ssn 139/udp Shell > grep -n ^imap /etc/services 129:imap 143/tcp imap2 # Interim Mail Access Proto v2 130:imap 143/udp imap2 168:imap3 220/tcp # Interactive Mail Access 169:imap3 220/udp # Protocol v3 260:imaps 993/tcp # IMAP over SSL 261:imaps 993/udp # IMAP over SSLIn other words, the content printed above is lines 123 to 129
- Print the line where the string is located and until the last line
Shell > cat /etc/services | sed -n '/^netbios/,$p'- Using variables in bash scripts
Shell > vim test1.sh #!/bin/bash a=10 sed -n ''${a}',$!p' /etc/services # or sed -n "${a},\$!p" /etc/services- Regular expression
Matches only "Three Digits" + "/udp".
Shell > cat /etc/services | sed -r -n '/[^0-9]([1-9]{3}\/udp)/p' sunrpc 111/udp portmapper rpcbind # RPC 4.0 portmapper UDP auth 113/udp authentication tap ident sftp 115/udp uucp-path 117/udp nntp 119/udp readnews untp # USENET News Transfer Protocol ntp 123/udp # Network Time Protocol netbios-ns 137/udp netbios-dgm 138/udp netbios-ssn 139/udp ... -
Match and delete (
d)It is similar to printing, except that the operation command is replaced with
dand the -n option is not required.- Delete all lines that match the udp string, and delete all comment lines, and delete all Blank line
Shell > sed -e '/udp/d' -e '/^#/d' -e '/^$/d' /etc/services tcpmux 1/tcp # TCP port service multiplexer rje 5/tcp # Remote Job Entry echo 7/tcp discard 9/tcp sink null systat 11/tcp users daytime 13/tcp qotd 17/tcp quote chargen 19/tcp ttytst source ftp-data 20/tcp ftp 21/tcp ssh 22/tcp # The Secure Shell (SSH) Protocol telnet 23/tcp ...- Delete consecutive lines of text
Shell > cat -n /etc/services | sed '10,$d' 1 # /etc/services: 2 # $Id: services,v 1.49 2017/08/18 12:43:23 ovasik Exp $ 3 # 4 # Network services, Internet style 5 # IANA services version: last updated 2016-07-08 6 # 7 # Note that it is presently the policy of IANA to assign a single well-known 8 # port number for both TCP and UDP; hence, most entries here have two entries 9 # even if the protocol doesn't support UDP operations.- Regular expression
Shell > cat /etc/services | sed -r '/(tcp)|(udp)|(^#)|(^$)/d' http 80/sctp # HyperText Transfer Protocol bgp 179/sctp https 443/sctp # http protocol over TLS/SSL h323hostcall 1720/sctp # H.323 Call Control nfs 2049/sctp nfsd shilp # Network File System rtmp 1/ddp # Routing Table Maintenance Protocol nbp 2/ddp # Name Binding Protocol echo 4/ddp # AppleTalk Echo Protocol zip 6/ddp # Zone Information Protocol discard 9/sctp # Discard discard 9/dccp # Discard SC:DISC ... -
Replace strings(
s///g)Syntax Syntax description sed 's/string/replace/g' FILENAMEs: All lines representing the content of the file. You can also specify the range of lines, for example: sed '20,200s/netbios/TMP/g' /etc/services
g (Global): If there is no g, This means that when multiple matching strings appear on a single line, only the first matching string will be replaced.
/: Delimiter style. You can also specify other styles, for example:sed '20,200s?netbios?TMP?g' /etc/servicesTip
Example in the bash script:
Shell > vim /root/sedReplace.sh #!/bin/bash a="SELINUX=enforcing" b="SELINUX=disabled" sed -i 's/'${a}'/'${b}'/g' /etc/selinux/config # or sed -i "s/${a}/${b}/g" /etc/selinux/config- Replace and print
Shell > sed -n '44,45s/ssh/SSH/gp' /etc/services SSH 22/tcp SSH 22/udpShell > sed -n '44,45s/ssh/&-SSH/gp' /etc/services ssh-SSH 22/tcp ssh-SSH 22/udp- Use a string to locate one or more lines and replace the specified string within the line range
Shell > grep ssh /etc/services -n 44:ssh 22/tcp # The Secure Shell (SSH) Protocol 45:ssh 22/udp # The Secure Shell (SSH) Protocol 551:x11-ssh-offset 6010/tcp # SSH X11 forwarding offset 593:ssh 22/sctp # SSH 1351:sshell 614/tcp # SSLshell 1352:sshell 614/udp # SSLshell 1607:netconf-ssh 830/tcp # NETCONF over SSH 1608:netconf-ssh 830/udp # NETCONF over SSH 7178:sdo-ssh 3897/tcp # Simple Distributed Objects over SSH 7179:sdo-ssh 3897/udp # Simple Distributed Objects over SSH 7791:netconf-ch-ssh 4334/tcp # NETCONF Call Home (SSH) 8473:snmpssh 5161/tcp # SNMP over SSH Transport Model 8474:snmpssh-trap 5162/tcp # SNMP Notification over SSH Transport Model 9126:tl1-ssh 6252/tcp # TL1 over SSH 9127:tl1-ssh 6252/udp # TL1 over SSH 10796:ssh-mgmt 17235/tcp # SSH Tectia Manager 10797:ssh-mgmt 17235/udp # SSH Tectia Manager Shell > sed '/ssh/s/tcp/TCP/gp' -n /etc/services ssh 22/TCP # The Secure Shell (SSH) Protocol x11-ssh-offset 6010/TCP # SSH X11 forwarding offset sshell 614/TCP # SSLshell netconf-ssh 830/TCP # NETCONF over SSH sdo-ssh 3897/TCP # Simple Distributed Objects over SSH netconf-ch-ssh 4334/TCP # NETCONF Call Home (SSH) snmpssh 5161/TCP # SNMP over SSH Transport Model snmpssh-trap 5162/TCP # SNMP Notification over SSH Transport Model tl1-ssh 6252/TCP # TL1 over SSH ssh-mgmt 17235/TCP # SSH Tectia Manager- String replacement for consecutive lines
Shell > sed '10,30s/tcp/TCP/g' /etc/services- Multiple matches and replacements
Shell > cat /etc/services | sed 's/netbios/test1/g ; s/^#//d ; s/dhcp/&t2/g'- Group replacement of regular expressions
In regular expressions, a "()" is a grouping. \1 represents reference group 1, \2 represents reference group 2, and so on.
Shell > cat /etc/services ... axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures Shell > cat /etc/services | sed -r 's/([0-9]*\/tcp)/\1\tCONTENT1/g ; s/([0-9]*\/udp)/\1\tADD2/g' ... axio-disc 35100/tcp CONTENT1 # Axiomatic discovery protocol axio-disc 35100/udp ADD2 # Axiomatic discovery protocol pmwebapi 44323/tcp CONTENT1 # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp ADD2 # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp CONTENT1 # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp CONTENT1 # Capture handwritten signatures\t: That is, a tab
- Replace all comment lines with blank space
Shell > cat /etc/services | sed -r 's/(^#.*)//g' ... chargen 19/udp ttytst source ftp-data 20/tcp ftp-data 20/udp ftp 21/tcp ftp 21/udp fsp fspd ssh 22/tcp # The Secure Shell (SSH) Protocol ssh 22/udp # The Secure Shell (SSH) Protocol ...- Replace one of the lowercase letters of a word with a capital letter
Shell > echo -e "hello,world\nPOSIX" | sed -r 's/(.*)w/\1W/g' hello,World POSIX- String position swapping
Shell > cat /etc/services ... cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signaturesWe can divide this file into five parts:
cloudcheck-ping 45514 / udp # ASSIA CloudCheck WiFi Management keepalive ↓ ↓ ↓ ↓ ↓ (.*) (\<[0-9]+\>) \/ (tcp|udp) (.*) ↓ ↓ ↓ ↓ \1 \2 \3 \4Shell > cat /etc/services | sed -r 's/(.*)(\<[0-9]+\>)\/(tcp|udp)(.*)/\1\3\/\2\4/g' ... edi_service udp/34567 # dhanalakshmi.org EDI Service axio-disc tcp/35100 # Axiomatic discovery protocol axio-disc udp/35100 # Axiomatic discovery protocol pmwebapi tcp/44323 # Performance Co-Pilot client HTTP API cloudcheck-ping udp/45514 # ASSIA CloudCheck WiFi Management keepalive cloudcheck tcp/45514 # ASSIA CloudCheck WiFi Management System spremotetablet tcp/46998 # Capture handwritten signatures- Remove any blank characters
Shell > echo -e "abcd\t1 2 3 4\tWorld" abcd 1 2 3 4 World Shell > echo -e "abcd\t1 2 3 4\tWorld" | sed -r 's/(\s)*//g' abcd1234World -
Execute multiple times using the -e option
The following example:
Shell > tail -n 10 /etc/services aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures Shell > tail -n 10 /etc/services | sed -e '1,3d' -e '/cloud/s/ping/PING/g' # or Shell > tail -n 10 /etc/services | sed '1,3d ; /cloud/s/ping/PING/g' edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-PING 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures -
Add content above or below a specific line (
ianda)- Add two lines of content above the specified line number
Shell > tail -n 10 /etc/services > /root/test.txt Shell > cat /root/test.txt aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures Shell > cat /root/test.txt | sed '3i 123\ abc' aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery 123 abc ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures- Add three lines below the specified line number
Shell > cat /root/test.txt | sed '5a 123\ comment yes\ tcp or udp' aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol 123 comment yes tcp or udp axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures- Match a specific line based on a string and add 2 lines of content above it
Shell > cat /root/test.txt | sed '/tcp/iTCP\ UDP' TCP UDP aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery TCP UDP ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service TCP UDP axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol TCP UDP pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive TCP UDP cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System TCP UDP spremotetablet 46998/tcp # Capture handwritten signatures -
Replace lines (
c)- Locate one or more lines based on a string and replace these lines of text
Shell > cat /root/test.txt | sed '/ser/c\TMP1 \ TMP2' TMP1 TMP2 ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery TMP1 TMP2 axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures- Single line replacement
Shell > cat /root/test.txt | sed '7c REPLACE' aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol REPLACE cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures- Replace consecutive lines of text
Shell > cat /root/test.txt | sed '2,$c REPLACE1 \ replace2' aigairserver 21221/tcp # Services for Air Server REPLACE1 replace2- Replace even numbered lines
Shell > cat /root/test.txt | sed '2~2c replace' aigairserver 21221/tcp # Services for Air Server replace ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery replace axio-disc 35100/tcp # Axiomatic discovery protocol replace pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API replace cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System replace -
Read the contents of the file and append its contents below the matching line (
r)Shell > cat /root/app.txt append1 POSIX UNIX Shell > cat /root/test.txt | sed '/ping/r /root/app.txt' aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive append1 POSIX UNIX cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures -
Write matching lines to other files (
w)Shell > cat /root/test.txt | sed '/axio/w /root/storage.txt' Shell > cat /root/storage.txt axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol -
Read/append the next line of input into the "pattern space" (
nandN)- Print the next line of the matching line
Shell > cat /root/test.txt aigairserver 21221/tcp # Services for Air Server ka-kdp 31016/udp # Kollective Agent Kollective Delivery ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery edi_service 34567/udp # dhanalakshmi.org EDI Service axio-disc 35100/tcp # Axiomatic discovery protocol axio-disc 35100/udp # Axiomatic discovery protocol pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System spremotetablet 46998/tcp # Capture handwritten signatures Shell > cat /root/test.txt | sed '/ping/{n;p}' -n cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management SystemTip
Multiple
sedoperation commands may affect each other, and you can use "{ }" to reduce this effect.- Print even text lines
First, read the first line, as an n command is present; the second line will be printed out, and so on.
Shell > cat -n /root/test.txt | sed -n '{n;p}' # or Shell > cat -n /root/test.txt | sed -n '2~2p' 2 ka-kdp 31016/udp # Kollective Agent Kollective Delivery 4 edi_service 34567/udp # dhanalakshmi.org EDI Service 6 axio-disc 35100/udp # Axiomatic discovery protocol 8 cloudcheck-ping 45514/udp # ASSIA CloudCheck WiFi Management keepalive 10 spremotetablet 46998/tcp # Capture handwritten signatures- Print odd text lines
Shell > cat -n /root/test.txt | sed -n '{p;n}' # or Shell > cat -n /root/test.txt | sed -n '1~2p' # or Shell > cat -n /root/test.txt | sed 'n;d' 1 aigairserver 21221/tcp # Services for Air Server 3 ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery 5 axio-disc 35100/tcp # Axiomatic discovery protocol 7 pmwebapi 44323/tcp # Performance Co-Pilot client HTTP API 9 cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management System- Print 3n lines
Shell > cat -n /root/test.txt | sed -n '{n;n;p}' # or Shell > cat -n /root/test.txt | sed -n '3~3p' 3 ka-sddp 31016/tcp # Kollective Agent Secure Distributed Delivery 6 axio-disc 35100/udp # Axiomatic discovery protocol 9 cloudcheck 45514/tcp # ASSIA CloudCheck WiFi Management SystemN
Read the first line and append one line after encountering the
Ncommand. In this example, the "pattern space" is "1\n2". Finally, execute theqcommand to exit.Shell > seq 1 10 | sed 'N;q' 1 2Because there is no additional line after line 9, the output is as follows:
Shell > seq 1 9 | sed -n 'N;p' 1 2 3 4 5 6 7 8When the last line is read, the
Ncommand is not executed and the output is as follows:Shell > seq 1 9 | sed -n '$!N;p' 1 2 3 4 5 6 7 8 9Merge two lines into one line. Replace the "\n" of the "pattern space" with a blank character.
Shell > seq 1 6 | sed 'N;{s/\n//g}' 12 34 56 -
Ignore case (
I)There seems to be no information about ignoring case in
man 1 sed.Shell > echo -e "abc\nAbc" | sed -n 's/a/X/Igp' Xbc XBCShell > cat /etc/services | sed '/OEM/Ip' -n oem-agent 3872/tcp # OEM Agent oem-agent 3872/udp # OEM Agent oemcacao-jmxmp 11172/tcp # OEM cacao JMX-remoting access point oemcacao-rmi 11174/tcp # OEM cacao rmi registry access point oemcacao-websvc 11175/tcp # OEM cacao web service access pointShell > cat /etc/services | sed -r '/(TCP)|(UDP)/Id'Shell > cat /etc/services | sed -r '/(TCP)|(UDP)/Ic TMP' -
Gets the total number of lines in a file
Shell > cat /etc/services | sed -n '$=' # or Shell > cat /etc/services | wc -l 11473
Author: tianci li