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Top Forums UNIX for Dummies Questions & Answers echo appends to a read-only file Post 302382333 by anand_bh on Wednesday 23rd of December 2009 04:41:23 AM
Old 12-23-2009
echo appends to a read-only file

echo command can append to a read-only file too.

If the file is read-only, with w flag removed, then even echo should not be able to append to the file. But it is possible.

Can anybody explain the below behaviour?

Code:
/root > echo 'sample text' > file
/root > cat file
sample text
/root > ls -l file
-r--r--r--  1 root  wheel  12 Dec 23 15:04 file
/root > chmod -w file
/root > ls -l file
-r--r--r--  1 root  wheel  12 Dec 23 15:04 file
/root > echo 'trying to append' >> file
/root > cat file
sample text
trying to append


Last edited by pludi; 12-23-2009 at 05:47 AM.. Reason: code tags, please...
 

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line(1) 						      General Commands Manual							   line(1)

NAME
line - Reads one line from standard input SYNOPSIS
line STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: line: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
None DESCRIPTION
The line command copies one line, up to and including a newline, from standard input and writes it to standard output. Use this command within a shell command file to read from your terminal. The line command always writes at least a newline character. NOTES
The line utility has no internationalization features and is marked LEGACY in XCU Issue 5. Use the read utility instead. EXIT STATUS
Success. End-of-File. EXAMPLES
To read a line from the keyboard and append it to a file, enter: echo 'Enter comments for the log:' echo ': c' line >>log This shell procedure displays the message: Enter comments for the log: It then reads a line of text from the keyboard and adds it to the end of the file log. The echo ': c' command displays a : (colon) prompt. See the echo command for information about the c escape sequence. SEE ALSO
Commands: echo(1), ksh(1), read(1), Bourne shell sh(1b), POSIX shell sh(1p) Functions: read(2) Standards: standards(5) line(1)
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