- Shell :#! /Bin/sh: No such file or directory
- PHP: Warning: Cannot modify header information-headers already sent
Before discussing in detail the problem of BOM detection and deletion in UTF-8 coding, we may try to warm up with an example:
- Shell> curl-s http://phone.jbxue.com/| head-1 | sed-n l
- \ 357 \ 273 \ 277// EN "" http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd "> \ r$
As shown above, the first three bytes are 357, 273, and 277, which are the BOM of the octal component.
- Shell> curl-s http://phone.jbxue.com/| head-1 | hexdump-C
- 00000000 ef bb bf 3c 21 44 4f 43 54 59 50 45 20 68 74 6d |...00000010 6c 20 50 55 42 4c 49 43 20 22 2d 2f 57 33 43 | l PUBLIC "-// W3C |
- 00000020 2f 2f 44 54 44 20 58 48 54 4d 4c 20 31 2e 30 20 | // dtd xhtml 1.0 |
- 00000030 54 72 61 6e 73 69 74 69 6f 6e 61 6c 2f 2f 45 4e | Transitional // EN |
- 00000040 22 20 22 68 74 70 3a 2f 2f 77 77 77 2e 77 33 | "" http: // www. w3 |
- 00000050 2e 6f 72 67 2f 54 52 2f 78 68 74 6d 6c 31 2f 44 |. org/TR/xhtml1/D |
- 00000060 54 44 2f 78 68 74 6d 6c 31 2d 74 72 61 6e 73 69 | TD/xhtml1-transi |
- 00000070 74 69 6f 6e 61 6c 2e 64 74 64 22 3e 0d 0a | tional. dtd ">... |
As shown above, the first three bytes are EF, BB, and BF, which are the hexadecimal BOM. Note: When a third-party website page is used, examples cannot be always available. In actual project development, may face hundreds of thousands of text files, if a few files mixed into the BOM, it is difficult to notice, if there is no BOM UTF-8 text file example, you can use vi to write a few, the relevant commands are as follows: # set the UTF-8 encoding: set fileencoding = UTF-8 # Add BOM: set bomb # delete BOM: set nobomb # Query BOM: set bomb? Inspect BOM in UTF-8 code
- Shell> grep-r-I-l $ '^ \ xEF \ xBB \ xBF'/path
Delete BOM from UTF-8 encoding
- Shell> grep-r-I-l $ '^ \ xEF \ xBB \ xBF'/path | xargs sed-I's/^ \ xEF \ xBB \ xBF //; q'
Recommendation: If SVN is used, you can add relevant code to the pre-commit hook to prevent BOM.
#! /Bin/sh REPOS = "$1" - TXN = "$2"
SVNLOOK =/usr/bin/svnlook FILES = '$ SVNLOOK changed-t "$ TXN" "$ REPOS" | awk'/^ [UA]/{print $2 }'' For FILE in $ FILES; do - If $ SVNLOOK cat-t "$ TXN" "$ REPOS" "$ FILE" | grep-q $ '^ \ xEF \ xBB \ xBF'; then
- Echo "Byte Order Mark be found in $ FILE" 1> & 2
- Exit 1
- Fi
- Done
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