Linux grep command operation guide

① Definition

Grep is a row-level device that analyzes a row of information. If there is any information we need, the whole row is returned.

② Function

Compares string data to print the strings that meet your needs.

③ Format

Grep [-acinv] [-- color = auto] 'query string' filename

Parameters:
-A: searches for data in the format of a binary file and a text file.
-C: calculates the number of times a 'query string' is found.
-I: case-insensitive
-N: Output row number
-V: displays the row without the 'query string' content.
-A: numbers can be added to the end, which means that, apart from listing the rows, the subsequent n rows are also listed.
-B: numbers can be added to the end, which means before. In addition to listing this row, the preceding n rows are also listed.
-- Color = Auto: Color of keywords

④ Example
Eg01: Identify the identifier of a checkpoint event

[oracle@localhost bdump]$ grep -in --color=auto 'checkpoint' alert_orcl.log64:  checkpoint is 44607466:  checkpoint is 44607469:  checkpoint is 44607472:  checkpoint is 446074383:  checkpoint is 4602001845:Checkpoint not complete2112:  checkpoint is 6062172114:  checkpoint is 6062172116:  checkpoint is 6062172118:  checkpoint is 6062172120:  checkpoint is 606217

Eg02: find information about the NIC from the kernel

[oracle@localhost bdump]$ dmesg | grep -n -A3 -B2 --color=auto 'eth'599-iscsi: registered transport (iser)600-iscsi: registered transport (be2iscsi)601:eth0: no IPv6 routers present602-Bluetooth: Core ver 2.10603-NET: Registered protocol family 31604-Bluetooth: HCI device and connection manager initialized--615-ip_conntrack version 2.4 (8192 buckets, 65536 max) - 228 bytes per conntrack616-ip6_tables: (C) 2000-2006 Netfilter Core Team617:peth0: Promiscuous mode enabled.618:device peth0 entered promiscuous mode619:xenbr0: port 1(peth0) entering forwarding state620-device vif0.0 entered promiscuous mode621-New device vif0.0 does not support netpoll622-Disabling netpoll for xenbr0--625-hdc: drive_cmd: error=0x04 { AbortedCommand }626-ide: failed opcode was: 0xec627:eth0: no IPv6 routers present628:xenbr0: port 1(peth0) entering disabled state629:xenbr0: port 1(peth0) entering forwarding state