Red Hat APPLICATION STACK 1.2 RELEASE Manuale Utente Scaricare il pdf (Pagina 29)

Chapter 5.

Command Line Tools

This section descibes the behavioral changes of command-line tools in Red Hat Enterprise Linux 6.

5.1. Grep

The behavior of the grep command has changed with regards to searching for upper and lower case

strings. Using interval searching in the [a-z] format is dependent on the LC_COLLATE variable.

You can set LC_COLLATE=C to preserve old behavior and to achieve proper results when performing

interval searching with this method; however, in Red Hat Enterprise Linux 6, the recommended way of

interval searching is to use the [[:lower:]],[[:upper:]] format.

This change can significantly affect output, so scripts and processes should be reviewed to continue to

achieve the correct results.

5.2. Sed

The sed command with the -i option lets you delete the contents of a read-only file and lets you

delete other protected files. The permissions on a file define what actions can take place to that

file, while the permissions on a directory define what actions can be taken to the list of files in that

directory. For this reason, sed does not let you use -i on a write-enabled file in a read-only directory,

and will break symbolic or hard links when the -i option is used on such a file.

5.3. Pcre

The pcre package has been updated to 7.8. It includes the following behavioral changes:

• UTF-8 checking now references RFC 3629 instead of RFC 2279. This makes it more restrictive

in the strings that it accepts. For example, the UTF-8 character ordinal value is now limited to

0x0010FFFF:

$ echo -ne "\x00\x11\xff\xff" | recode UCS-4-BE..UTF8 | pcregrep --utf-8 '.'

pcregrep: pcre_exec() error -10 while matching this line:

Please refer to the RFC for more details: http://tools.ietf.org/html/rfc3629#section-12.

• Saved patterns that were compiled by earlier versions of PCRE must be recompiled. This affects

applications that serialize precompiled PCRE expressions to external memory (for example, a file)

and load them later. This is usually done for performance reasons, for example in large spam filters.

5.4. Shells

The location of the shell binary files has changed. For example, the bash and ksh binaries are no

longer in /usr/bin. Both binaries are now found in /bin. Scripts will require updating to point to the

new location of the binary.

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Red Hat APPLICATION STACK 1.2 RELEASE Manuale Utente Pagina 29