pushBack                package:base                R Documentation

_P_u_s_h _T_e_x_t _B_a_c_k _o_n _t_o _a _C_o_n_n_e_c_t_i_o_n

_D_e_s_c_r_i_p_t_i_o_n:

     Functions to push back text lines onto a connection, and to
     enquire how many lines are currently pushed back.

_U_s_a_g_e:

     pushBack(data, connection, newLine = TRUE)
     pushBackLength(connection)

_A_r_g_u_m_e_n_t_s:

    data: a character vector.

connection: A connection.

 newLine: logical. If true, a newline is appended to each string pushed
          back.

_D_e_t_a_i_l_s:

     Several character strings can be pushed back on one or more
     occasions. The occasions form a stack, so the first line to be
     retrieved will be the first string from the last call to
     `pushBack'.  Lines which are pushed back are read prior to the
     normal input from the connection, by the normal text-reading
     functions such as `readLines' and `scan'.

     Pushback is only allowed for readable connections.

_V_a_l_u_e:

     `pushBack' returns nothing.

     `pushBackLength' returns number of lines currently pushed back.

_S_e_e _A_l_s_o:

     `connection', `readLines'.

_E_x_a_m_p_l_e_s:

     zz <- textConnection(LETTERS)
     readLines(zz, 2)
     pushBack(c("aa", "bb"), zz)
     pushBackLength(zz)
     readLines(zz, 1)
     pushBackLength(zz)
     readLines(zz, 1)
     readLines(zz, 1)
     close(zz)

