README.md

@@ -1145,29 +1145,6 @@ date --date @1615852800
 
 ```
 
-##### Print current time point for N days ago or N days after
-```bash
-# print current date first (for the following example)
-date +"%F %H:%M:%S"
-# 2023-03-11 16:17:09
-
-# print the time that is 1 day ago
-date -d"1 day ago" +"%F %H:%M:%S"
-# 2023-03-10 16:17:09
-
-# print the time that is 7 days ago
-date -d"7 days ago" +"%F %H:%M:%S"
-# 2023-03-04 16:17:09
-
-# print the time that is a week ago
-date -d"1 week ago" +"%F %H:%M:%S"
-# 2023-03-04 16:17:09
-
-# add 1 day to date
-date -d"-1 day ago" +"%F %H:%M:%S"
-# 2023-03-12 16:17:09
-```
-
 ##### wait for random duration (e.g. sleep 1-5 second, like adding a jitter)
 ```bash
 sleep $[ ( $RANDOM % 5 ) + 1 ]
@@ -2860,28 +2837,12 @@ var=$((var+1))
 cat filename|rev|cut -f1|rev
 ```
 
-##### Create or replace a file with contents
+##### Cat to a file
 ```bash
 cat >myfile
 let me add sth here
-# exit with ctrl+d
-
-# or using tee
-tee myfile
-let me add sth else here
-# exit with ctrl+d
-```
-
-##### Append to a file with contents
-```bash
-cat >>myfile
-let me add sth here
-# exit with ctrl+d
-
-# or using tee
-tee -a myfile
-let me add sth else here
-# exit with ctrl+d
+exit by control + c
+^C
 ```
 
 ##### Clear the contents of a file (e.g. filename)
@@ -3279,9 +3240,9 @@ fallocate -l 10G 10Gigfile
 
 ##### Create dummy file of certain size (e.g. 200mb)
 ```bash
-dd if=/dev/zero of=/dev/shm/200m bs=1024k count=200
+dd if=/dev/zero of=//dev/shm/200m bs=1024k count=200
 # or
-dd if=/dev/zero of=/dev/shm/200m bs=1M count=200
+dd if=/dev/zero of=//dev/shm/200m bs=1M count=200
 
 # Standard output:
 # 200+0 records in
@@ -3294,29 +3255,9 @@ dd if=/dev/zero of=/dev/shm/200m bs=1M count=200
 watch -n 1 wc -l filename
 ```
 
-##### Use Bash Strict Mode
-```bash
-# These options can make your code safer but, depending on how your pipeline is written, it might be too aggressive 
-# or it might not catch the errors that you are interested in
-
-# for reference see https://gist.github.com/mohanpedala/1e2ff5661761d3abd0385e8223e16425
-#               and https://mywiki.wooledge.org/BashPitfalls#set_-euo_pipefail
-
-set -o errexit      # exit immediately if a pipeline returns a non-zero status
-set -o errtrace     # trap ERR from shell functions, command substitutions, and commands from subshell
-set -o nounset      # treat unset variables as an error
-set -o pipefail     # pipe will exit with last non-zero status, if applicable
-set -Eue -o pipefail  # shorthand for above (pipefail has no short option)
-```
-
 ##### Print commands and their arguments when execute (e.g. echo `expr 10 + 20 `)
 ```bash
 set -x; echo `expr 10 + 20 `
-# or
-set -o xtrace; echo `expr 10 + 20 `
-
-# to turn it off..
-set +x
 ```
 
 ##### Print some meaningful sentences to you (install fortune first)