RTEMS GNU Tools On-Line Library

Output

Debugging with GDB

16.4: Commands for controlled output

During the execution of a command file or a user-defined command, normal GDB output is suppressed; the only output that appears is what is explicitly printed by the commands in the definition. This section describes three commands useful for generating exactly the output you want.

echo text

Print text. Nonprinting characters can be included in text using C escape sequences, such as `\n' to print a newline. No newline is printed unless you specify one. In addition to the standard C escape sequences, a backslash followed by a space stands for a space. This is useful for displaying a string with spaces at the beginning or the end, since leading and trailing spaces are otherwise trimmed from all arguments. To print ` and foo = ', use the command `echo \ and foo = \ '.

A backslash at the end of text can be used, as in C, to continue the command onto subsequent lines. For example,

echo This is some text\n\
which is continued\n\
onto several lines.\n

produces the same output as

echo This is some text\n
echo which is continued\n
echo onto several lines.\n

output expression

Print the value of expression and nothing but that value: no newlines, no `$nn = '. The value is not entered in the value history either. See Expressions, for more information on expressions.

output/fmt expression

Print the value of expression in format fmt. You can use the same formats as for print. See Output Formats, for more information.

printf string, expressions...

Print the values of the expressions under the control of string. The expressions are separated by commas and may be either numbers or pointers. Their values are printed as specified by string, exactly as if your program were to execute the C subroutine

printf (string, expressions...);

For example, you can print two values in hex like this:

printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo

The only backslash-escape sequences that you can use in the format string are the simple ones that consist of backslash followed by a letter.

Debugging with GDB