From 4823b8018688092416b3cd4ba9f4f7f86789eedd Mon Sep 17 00:00:00 2001 From: johannst Date: Tue, 12 Dec 2023 23:48:13 +0000 Subject: deploy: 4ed29d46d45a751071d89be37c87de71204efda4 --- tools/awk.html | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) (limited to 'tools/awk.html') diff --git a/tools/awk.html b/tools/awk.html index efd30b7..3da3746 100644 --- a/tools/awk.html +++ b/tools/awk.html @@ -90,7 +90,9 @@
  1. Introduction
  2. Tools
    1. zsh
    2. bash
    3. fish
    4. tmux
    5. git
    6. awk
    7. emacs
    8. gpg
    9. gdb
    10. gdbserver
    11. radare2
    12. qemu
    13. pacman
    14. dot
  4. Resource analysis & monitor
    1. lsof
    2. ss
    3. pidstat
    4. pgrep
    5. pmap
    6. pstack
  6. Trace and Profile
    1. strace
    2. ltrace
    3. perf
    4. OProfile
    5. time
  8. Binary
    1. od
    2. xxd
    3. readelf
    4. objdump
    5. nm
  10. Development
    1. c++filt
    2. c++
    3. glibc
    4. gcc
    5. cmake
    6. make
    7. ld.so
    8. symbol versioning
    9. python
    10. gcov
    11. pgo
  12. Linux
    1. systemd
    2. coredump
    3. ptrace_scope
    4. cryptsetup
    5. swap
    6. input
    7. acl
    8. zfs
  14. Network
    1. tcpdump
    2. firewall-cmd
    3. nftables
  16. Web
    1. html
    2. css
    3. chartjs
  18. Arch
    1. x86_64
    2. arm64
    3. armv7
    4. riscv
- + @@ -213,6 +215,10 @@ record ----> ∀ pattern matched fields ----> run associated action

Any valid awk expr can be a pattern.

+

An example is the regex pattern /abc/ { print $1 } which prints the first +field if the record matches the regex /abc/. This form is actually a short +version for $0 ~ /abc/ { print $1 }, see the regex comparison operator +below.

Special pattern

awk provides two special patterns, BEGIN and END, which can be used multiple times. Actions with those patterns are executed exactly once.

@@ -263,6 +269,15 @@ but this is a function and return value can be assigned to a variable.

  • %T alias for %H:%M:%S
    • +
  • +

    S ~ R, S !~ R

    +

    The regex comparison operator, where the former returns true if the string +S matches the regex R, and the latter is the negated form. +The regex can be either a +constant +or dynamic +regex.

    +

    • Examples

    Filter records

    @@ -274,6 +289,18 @@ prints the whole record.

    awk '!/^#/ { print $1 }' <file>

    Matches records not starting with #.

    +

    Range patterns

    +
    echo -e "a\nFOO\nb\nc\nBAR\nd" | \
+    awk '/FOO/,/BAR/ { print }'
+
    +

    /FOO/,/BAR/ define a range pattern of begin_pattern, end_pattern. When +begin_pattern is matched the range is turned on and when the +end_pattern is matched the range is turned off. This matches every record +in the range inclusive.

    +

    An exclusive range must be handled explicitly, for example as follows.

    +
    echo -e "a\nFOO\nb\nc\nBAR\nd" | \
+    awk '/FOO/,/BAR/ { if (!($1 ~ "FOO") && !($1 ~ "BAR")) { print } }'
+

    Access last fields in records

    echo 'a b c d e f' | awk '{ print $NF $(NF-1) }'
    -- cgit v1.2.3