How to pass arguments with special characters to c

Question

Calling .sh(shell script) with the required parameters as below :-

sh home/example.sh --context_param dbUserName=username --context_param dbPassword=exam!ple##### --context_param resultDate=2017-01-13

calling example.sh with paramters dbUsername and password but getting following error:-

-bash: !ple#####: event not found

I think special characters restrict the command to execute. Then how i have to pass the special characters. Any help will be appreciable.

Answer 1

You can do the following two things:

1. Escape every single special symbol with a backslash

   sh home/example.sh --context_param dbUserName=username --context_param dbPassword=exam\!ple\#\#\#\#\# --context_param resultDate=2017-01-13
   

2. Singlequote the entire argument.

   sh home/example.sh --context_param dbUserName=username --context_param dbPassword='exam!ple#####' --context_param resultDate=2017-01-13
   

From man bash

QUOTING

Quoting is used to remove the special meaning of certain characters or words to the shell. Quoting can be used to disable special treatment for special characters, to prevent reserved words from being recognized as such, and to prevent parameter expansion.

When the command history expansion facilities are being used, the history expansion character,usually !,must be quoted to prevent history expansion.

There are three quoting mechanisms: the escape character, single quotes, and double quotes.

A non-quoted backslash (\) is the escape character. It preserves the literal value of the next character that follows, with the exception of <newline>. If a \<newline> pair appears, and the backslash is not itself quoted, the \<newline> is treated as a line continuation (that is, it is removed from the input stream and effectively ignored).

Enclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.

Enclosing characters in double quotes preserves the literal value of all characters within the quotes, with the exception of $,`,\, and, when history expansion is enabled, !. The characters $ and ` retain their special meaning within double quotes. The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or <newline>. A double quote may be quoted within double quotes by preceding it with a backslash. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using a backslash. The backslash preceding the ! is not removed.

The special parameters * and @ have special meaning when in double quotes.

Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard.

Backslash escape sequences, if present, are decoded as follows:

          \a     alert (bell)
          \b     backspace
          \e
          \E     an escape character
          \f     form feed
          \n     new line
          \r     carriage return
          \t     horizontal tab
          \v     vertical tab
          \\     backslash
          \'     single quote
          \"     double quote
          \nnn   the eight-bit character whose value is the octal value nnn (one to three digits)
          \xHH   the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
          \uHHHH the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)
          \UHHHHHHHH
                 the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight hex digits)
          \cx    a control-x character

The expanded result is single-quoted, as if the dollar sign had not been present.

A double-quoted string preceded by a dollar sign ($"string") will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted.

Answer 2

Change the line,

dbPassword=exam!ple#####

to,

dbPassword='exam!ple#####'

to avoid ! (history-expansion) being treated specially in bash

From man bash under QUOTING sub-section,

When the command history expansion facilities are being used (see HISTORY EXPANSION below), the history expansion character, usually !, must be quoted to prevent history expansion.

more under HISTORY EXPANSION

History expansions are introduced by the appearance of the history expansion character, which is ! by default. Only backslash (\) and single quotes can quote the history expansion character.

Also, it is a good practice to quote all your name-value pairs to prevent Word-splitting done by shell.

sh home/example.sh --context_param dbUserName="username" --context_param dbPassword='exam!ple#####' --context_param resultDate="2017-01-13"

About word-splitting, from the man page,

Word Splitting

The shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not occur within double quotes for word splitting. The shell treats each character of IFS as a delimiter, and splits the results of the other expansions into words using these characters as field terminators

Answer 3

Pass it like this:

exam\!ple\#\#\#\#\#

Test:

echo exam\!ple\#\#\#\#\#