tr是UNIX的一个实用命令，用于转换，删除，删除重复字符。它从STDIN读取输入，然后输出结果到STDOUT。
tr is an UNIX utility for translating, or deleting, or squeezing repeated characters. It will read from STDIN and write to STDOUT.
tr stands for translate.
Syntax
The syntax of tr command is:
$ tr [OPTION] SET1 [SET2]
Translation
If both the SET1 and SET2 are specified and ?d?OPTION is not specified, then tr command will replace each characters in SET1 with each character in same position in SET2.
1. 转换字母大小写
1. Convert lower case to upper case
The following tr command is used to convert the lower case to upper case
$ tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
thegeekstuff
THEGEEKSTUFF
The following command will also convert lower case to upper case
$ tr [:lower:] [:upper:]
thegeekstuff
THEGEEKSTUFF
You can also use ranges in tr. The following command uses ranges to convert lower to upper case.
$ tr a-z A-Z
thegeekstuff
THEGEEKSTUFF
2.转换括号
2. Translate braces into parenthesis
You can also translate from and to a file. In this example we will translate braces in a file with parenthesis.
$ tr '{}' '()' < inputfile > outputfile
The above command will read each character from input file, translate if it is a brace, and write the output in output file.
3. 转换空白字符为TAB
3. Translate white-space to tabs
The following command will translate all the white-space to tabs
$ echo "This is for testing" | tr [:space:] '\t'
This is for testing
4.删除连续重复的字符
4. Squeeze repetition of characters using -s
In Example 3, we see how to translate space with tabs. But if there are two are more spaces present continuously, then the previous command will translate each spaces to a tab as follows.
$ echo "This is for testing" | tr [:space:] '\t'
This is for testing
We can use -s option to squeeze the repetition of characters.
$ echo "This is for testing" | tr -s [:space:] '\t'
This is for testing
Similarly you can convert multiple continuous spaces with a single space
$ echo "This is for testing" | tr -s [:space:] ' '
This is for testing
5. 删除指定的字符
5. Delete specified characters using -d option
tr can also be used to remove particular characters using -d option.
$ echo "the geek stuff" | tr -d 't'
he geek suff
To remove all the digits from the string, use
$ echo "my username is 432234" | tr -d [:digit:]
my username is
Also, if you like to delete lines from file, you can use sed d command.
6.排除指定的字符集
6. Complement the sets using -c option
You can complement the SET1 using -c option. For example, to remove all characters except digits, you can use the following.
$ echo "my username is 432234" | tr -cd [:digit:]
432234
7.从文件中删除所有不可打印的字符
7. Remove all non-printable character from a file
The following command can be used to remove all non-printable characters from a file.
$ tr -cd [:print:] < file.txt
8. Join all the lines in a file into a single line
The below command will translate all newlines into spaces and make the result as a single line.
$ tr -s '\n' ' ' < file.txt
Below command will list of all users listed in the access log and then sort them alphabetically
$ cat /var/log/squid/access.log | tr -s ' ' | cut -d ' ' -f 13 |sort |uniq
tr is an UNIX utility for translating, or deleting, or squeezing repeated characters. It will read from STDIN and write to STDOUT.
tr stands for translate.
Syntax
The syntax of tr command is:
$ tr [OPTION] SET1 [SET2]
Translation
If both the SET1 and SET2 are specified and ?d?OPTION is not specified, then tr command will replace each characters in SET1 with each character in same position in SET2.
1. 转换字母大小写
1. Convert lower case to upper case
The following tr command is used to convert the lower case to upper case
$ tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
thegeekstuff
THEGEEKSTUFF
The following command will also convert lower case to upper case
$ tr [:lower:] [:upper:]
thegeekstuff
THEGEEKSTUFF
You can also use ranges in tr. The following command uses ranges to convert lower to upper case.
$ tr a-z A-Z
thegeekstuff
THEGEEKSTUFF
2.转换括号
2. Translate braces into parenthesis
You can also translate from and to a file. In this example we will translate braces in a file with parenthesis.
$ tr '{}' '()' < inputfile > outputfile
The above command will read each character from input file, translate if it is a brace, and write the output in output file.
3. 转换空白字符为TAB
3. Translate white-space to tabs
The following command will translate all the white-space to tabs
$ echo "This is for testing" | tr [:space:] '\t'
This is for testing
4.删除连续重复的字符
4. Squeeze repetition of characters using -s
In Example 3, we see how to translate space with tabs. But if there are two are more spaces present continuously, then the previous command will translate each spaces to a tab as follows.
$ echo "This is for testing" | tr [:space:] '\t'
This is for testing
We can use -s option to squeeze the repetition of characters.
$ echo "This is for testing" | tr -s [:space:] '\t'
This is for testing
Similarly you can convert multiple continuous spaces with a single space
$ echo "This is for testing" | tr -s [:space:] ' '
This is for testing
5. 删除指定的字符
5. Delete specified characters using -d option
tr can also be used to remove particular characters using -d option.
$ echo "the geek stuff" | tr -d 't'
he geek suff
To remove all the digits from the string, use
$ echo "my username is 432234" | tr -d [:digit:]
my username is
Also, if you like to delete lines from file, you can use sed d command.
6.排除指定的字符集
6. Complement the sets using -c option
You can complement the SET1 using -c option. For example, to remove all characters except digits, you can use the following.
$ echo "my username is 432234" | tr -cd [:digit:]
432234
7.从文件中删除所有不可打印的字符
7. Remove all non-printable character from a file
The following command can be used to remove all non-printable characters from a file.
$ tr -cd [:print:] < file.txt
8. Join all the lines in a file into a single line
The below command will translate all newlines into spaces and make the result as a single line.
$ tr -s '\n' ' ' < file.txt
Below command will list of all users listed in the access log and then sort them alphabetically
$ cat /var/log/squid/access.log | tr -s ' ' | cut -d ' ' -f 13 |sort |uniq
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