test -f /etc/fstab ## true if a regular file test -h /etc/rc.local ## true if a symbolic link [ -x "$HOME/bin/hw" ] ## true if you can execute the file [[ -s $HOME/bin/hw ]] ## true if the file exists and is not empty 整数测试 整数之间的比较使用-eq、-ne、-gt...
in FROM. NULL is returned if there is no spec. The address of ERROR_POINTER is returned if the word specified cannot be found. CALLER_INDEX is the offset in SPEC to start looking; it is updated to point to just after the last character parsed. */staticchar*get_history_word_specifier(s...
First this program will print “Start program”, then the IF statement will check if the conditional expression[[ $1 -eq 4 ]]is true. It will only be true if you provide4as the first argument to the script. If the conditional expression if true then it will execute the code in betwee...
我在网上发现的处理错误的最好例子是由WilliamShotts,Jr在http://www.linuxcommand.org上写的。 他建议在bash中使用以下函数进行错误处理: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 #!/bin/bash # A slicker error handling routine # I ...
反斜槓轉義序列,如果存在的話,將做如下轉換: \a alert (bell) 響鈴 \b backspace 回退 \e an escape character 字符 Esc \f form feed 進紙 \n new line 新行符 \r carriage return 回車 \t horizontal tab 水平跳格 \v vertical tab 豎直跳格 \\ backslash 反斜槓 \' single quote 單引號 \nnn ...
printf "\n": This line prints a newline character to ensure the next output starts on a new line. if [ "$user_password" = "$my_password" ]; then: This line starts a conditional statement that checks if the entered password ('$user_password') matches the predefined password ('$my_...
awk substr example What is awk print $1? Sed Command in unix Remove Newline from String in Bash Replace Character in String in Bash Generate Random String in Bash Run String as Command in Bash Remove Double Quotes from String in Bash Bash Remove Special Characters from StringShare...
一个未被引用的反斜杠 (\) 是转义字符 escape character。 它保留其后下一个字符的字面意义,除非那是一个新行 符。 如果 \ 和新行符成对出现,并且反斜杠自身没有被引用,那么 \<newline> 被视为续行标志 (意思是,它被从输 入流中删除并忽略了)。 将字符放在单引号之中,将保留引用中所有字符的字面意义...
This is due to historical reasons as the braces are reserved words and can only be recognized as such when they are separated from the command list by whitespace or another shell metacharacter. Also when using the braces notation, you must terminate the last command by a semi-colon ;, an ...
A text file can contain different types of numeric and character data. Same data can be stored multiple times in a text file. Sometimes, you may require reading any text file by omitting duplicate lines of data. Bash uniq command is a useful command line utility tool that is used to read...