n>> file Direct file descriptor n to file; append to file if it already exists. n>& Duplicate standard output to file descriptor n. n<& Duplicate standard input from file descriptor n. n>&m File descriptor n is
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If you want to write multiple lines to a file, use the Here document (Heredoc) redirection. For example, you can pass the content to the cat command and write it to a file: cat << EOF > file.txt The current working directory is: $PWD You are logged in as $(whoami) EOF CopyTo...
Here, we list some basic bash syntax with a brief explanation. It is a good starting point if you are a beginner.
If the file exists, it is truncated to zero length. Otherwise, the file is created. Be extra careful when using this operator as you may overwrite an important file. The >> redirection operator appends the output to a given file. The file is created if it does not exist. You need to...
# If not running interactively, don't do anythingcase$-in*i*) ;;*) return;;esac# don't put duplicate lines or lines starting with space in the history.# See bash(1)formoreoptions HISTCONTROL=ignoreboth # append to the historyfile, don't overwrite itshopt -s histappend ...
7.1.1.1. 和if使用的表达式 下表包含了一个组成 TEST-COMMAND 命令或者命令列表,称作 “要素primaries” 的概览。这些primaries放置在方括号中来表示一个条件表达式的测试。 表 7.1. 主表达式Primary 意义 [ -a FILE ] 如果 FILE 存在则为真。 [ -b FILE ] 如果 FILE 存在且是一个块特殊文件则为真。
z Like SPACE, but if N is specified, it becomes the new window size. ESC-SPACE Like SPACE, but scrolls a full screenful, even if it reaches end-of-file in the process. ENTER or RETURN or ^N or e or ^E or j or ^J Scroll forward N lines, default 1. The entire N lines are...
To create a new file, you need to run the touch command followed by the name of the file. For example,$ touch hello.txtIt will create an empty file called "hello.txt" in the current directory. Use the ls command to verify if the file has been created or not.Advertisement - This ...
# PID of last background task $$ # PID of shell $0 # Filename of the shell script $_ # Last argument of the previous command 检查命令返回值 if ping -c 1 google.com; then echo "It appears you have a working internet connection" fi 检查grep 的返回值 if grep -q 'foo' ~/.bash_...