bash Pocket Reference

Syntax

This section describes the many symbols peculiar to the shell. The topics are arranged as follows:

• Special files

• Filename metacharacters

• Brace expansion

• Quoting

• Command forms

• Redirection forms

Special Files

The shell reads one or more startup files. Some of the files are read only when a shell is a login shell. Bash reads these files:

1. /etc/profile. Executed automatically at login.

2. The first file found from this list: ~/.bash_profile, ~/.bash_login, or ~/.profile. Executed automatically at login.

3. ~/.bashrc is read by every nonlogin shell. However, if invoked as sh, Bash instead reads $ENV, for POSIX compatibility.

The getpwnam() and getpwuid() functions are the sources of home directories for ~name abbreviations. (On personal systems, the user database is stored in /etc/passwd. However, on networked systems, this information may come from NIS, NIS+, or LDAP, not your workstation password file.)

Filename Metacharacters

*	Match any string of zero or more characters.
?	Match any single character.
[abc…]	Match any one of the enclosed characters; a hyphen can specify a range (e.g., a-z, A-Z, 0–9).
[!abc…]	Match any character not enclosed as above.
~	Home directory of the current user.
~name	Home directory of user name.
~+	Current working directory ($PWD).
~-	Previous working directory ($OLDPWD).

With the extglob option on:

?(pattern)	Match zero or one instance of pattern.
*(pattern)	Match zero or more instances of pattern.
+(pattern)	Match one or more instances of pattern ...